Theresa May – what lies beyond the public image?

There are the shoes, of course. Despite the fact that Theresa May is among the most senior politicians in Britain and is now the longest-serving home secretary for more than 50 years, it is the shoes that come most immediately to some people's minds when you mention her name. So let's get them out of the way…

The leopard-print kitten heels she wore as party chairman while delivering a blistering 2002 speech in which she warned that the Conservatives were viewed as "the nasty party". The patent over-the-knee boots she sported as home secretary to greet the president of the Republic of Korea on her 2013 state visit. The Russell & Bromley brogues with discreetly jewel-studded heels she wore on stage at last year's party conference. The red wedges. The zebra-print heels. The snakeskin court shoes. The list goes on.

Perhaps it's a function of the lack of female representation in the Houses of Parliament: a woman MP is rare enough, but one who chooses to indulge in such apparent fripperies and still demands to be taken seriously is enough to send us into an existential tailspin. When a handful of female MPs were appointed to new positions as part of a government reshuffle earlier this month, their outfits were analysed as part of what one newspaper called "the Downing Street Catwalk".

For the 57-year-old May, such attention is nothing new. She has become used to her footwear being endlessly dissected by pundits as if it might offer some dazzling insight into her state of mind. Two months ago, May's delivery of an uncompromising speech to the Police Federation, in which she pledged to break their power and warned that a string of corruption allegations risked destroying the very foundations of British policing, was notable not just for its content but also for the fact that her shoes, for once, did not seem to merit a mention in media reports.

"Oh, the shoes!" exclaims Sam Olsen, her campaign manager for the 2005 election, rolling his eyes. "The shoes are a leopard-print curse because she's now expected to wear them all the time."

He recalls hours spent on the road with May as she knocked on doors, wooing potential voters in her Maidenhead constituency. She would wear comfortable shoes in the car and then change into a pair of heels before emerging. Otherwise, Olsen says, "if she turned up at a meeting and she wasn't wearing them, the first thing people would say is, 'Where are the shoes, Theresa?'"

A former colleague says May remains unapologetic about her fashion choices. "She doesn't mind wearing something other people wouldn't expect her to wear. It's not an attention-seeking thing, it's defiant: 'I know I have a brain and I'm serious so I can wear pretty shoes'."

Does she care what other people think of her?

"No," comes the answer. "Not at all."

Theresa May, the sober-minded politician who also happens to like shoes, is a woman in the ascendant. She started out stuffing envelopes at her local Conservative Association before going on to become a councillor in the London borough of Merton in 1986. Elected to parliament in 1997, May was made the first female chairman of the Tory party in 2002. In the 2010 election, she more than doubled her majority in Maidenhead to 16,769. David Cameron responded by appointing her home secretary – only the fourth woman to hold one of the four great offices of state and the second female to take on the post.

When the prime minister reshuffled his cabinet a couple of weeks ago, May was among the few heavyweights to keep her job. Despite an obvious attempt to bring more diversity into the heart of government, May remains one of only five women who are full cabinet members.

Since being given the Home Office, she has tackled a number of thorny issues, some more successfully than others. The first of these is immigration. The Conservatives have pledged to bring net migration to the UK down to the tens of thousands by the next general election. May has weathered a string of Passport Office and border control fiascos but that target still remains elusive, despite her claims that 70,000 fewer people emigrated to Britain last year than in 2010.

Her second challenge has been Islamic extremism. She managed to get Abu Hamza deported and has banned a clutch of so-called hate preachers from entering the UK. In July 2013, she took on the European Court of Human Rights and negotiated an extradition treaty with Jordan that saw the deportation of the radical preacher Abu Qatada after two decades of resistance. This, in spite of the fact that the home secretary was shown to have mistakenly believed that Qatada's deadline for appeals ended 24 hours earlier than it actually did.

More recently, May has tackled head-on the might of the Police Federation (a move that was either brave or foolhardy, depending on your point of view) and spearheaded the setting up of a child abuse inquiry into historic allegations of paedophilia in Westminster. May's appointment of Baroness Butler-Sloss was roundly condemned when it emerged her brother, the late Sir Michael Havers, had been attorney general at the time of the alleged abuses in the 1980s. Butler-Sloss chose to stand down. Last week, she announced a public inquiry into the death of Russian dissident Alexander Litvinenko and the creation of a government unit to tackle the problem of female genital mutilation.

"She's done well as home secretary because she's basically stayed in the job," says a government source. "Her capabilities and her strengths are in managing crises."

Now May is openly being talked about as a potential Conservative leader. In a recent Ipsos Mori poll, 30% of respondents said they believed the home secretary had what it takes to be a future prime minister, ahead of her closest Conservative rival – the chancellor, George Osborne, on 18% – and only just behind the mayor of London, Boris Johnson, on 32%.

"She's been a frontline politician for 14 or 15 years and is pretty much the finished article," says Phillip Lee, the MP for Bracknell, the neighbouring constituency to May's. "She's able to be as decisive as she is because she's actually thought about this over a period of years."

In an era when politics has been tarnished by decades of scandal and spin, May seems to represent a more decent, less personality-focused approach. She comes across as straightforward, shrewd and reassuringly staid. Unlike Tony Blair or David Cameron, she does not schmooze.

"She doesn't flirt," says a male Conservative MP who, like many others I speak to, does not want to be quoted on the record for fear of stoking talk around any leadership bid this close to an election. "She doesn't use sex as a weapon. Thatcher did, by all accounts. Theresa is almost asexual. I think we're dealing with a mature, wise, experienced and competent politician but what she lacks, I think, is warmth and personality on first meeting."

Several times, over the course of my conversations with her friends, colleagues and fellow MPs, a comparison is drawn with the German chancellor, Angela Merkel. Merkel, like May, is seen as a safe pair of hands: stolid, reliable but also clear-sighted enough to make difficult choices.

And in a political party that struggles to shake off its elitist, old Etonian, yah-boo-sucks reputation, May represents a different kind of politician: a calm headmistress in a chamber full of over-excitable public school boys. She holds herself at one remove. As party chairman, she refused to take up honorary membership of the Carlton Club, that bastion of traditional Conservatism. She is an unapologetic feminist (once posing in a Fawcett Society T-shirt emblazoned with the statement: "This is what a feminist looks like") and co-founded Women2Win in 2006 with Anne (now Baroness) Jenkin to increase the number of Conservative women in parliament.

According to a former colleague: "She's not going to be part of any boys' club because a) she's not a boy and b) she wouldn't want to be a member of any club anyway… I don't think she would ever want to be seen to make her sex an excuse for anything. She didn't treat me as a woman, she treated me as a person. Her beef with Harriet Harman [the Labour deputy leader] is 'Don't play victim'. You just do your job really well and then you can punch at the same weight a man can."

Her obdurate stance has earned her some vociferous critics. There are those who claim that, while she takes care never to sully her own hands with the grubby business of political backstabbing, she will send out her team to issue ferocious briefings against her rivals. There have been well-publicised feuds with some big cabinet beasts. The first was Kenneth Clarke, the former justice secretary. May claimed he was too soft on crime and is said to have briefed accordingly. Clarke accused her of being "laughable and childlike" after she condemned the Human Rights Act in 2011 (erroneously stating that an illegal immigrant had not been deported because he had a pet cat).

More recently, there was a clash with Michael Gove about the correct way to fight Islamic extremism, which resulted in public embarrassment for the prime minister, who demanded that May sack her trusted special adviser, Fiona Cunningham. Relations between the Home Office and Number 10 are now said to be "very bad".

"Her working style and that of her team is very closed, very controlling, very untrusting," says the same Tory source. "They don't share. They see conspiracies around every corner and think everyone is either briefing against or undermining them, so they brief first. That's their operating style… it's just a pain in the arse."

And yet May wins a grudging respect for her refusal to play the game. "There is a steeliness to her which is impressive," continues the source. "One of the things I admire about her is that you know you don't mess with her. David Cameron knows it's a minister who is going to fight back a bit."

Simon Danczuk, the Labour MP for Rochdale who has been instrumental in setting up the Westminster child abuse inquiry, which is overseen by May, says she is "an extremely professional, smart woman. She's very clever and she really listens to what people have to say". But he adds: "She comes across as quite cold, whereas David Cameron – for all his faults, you'd go for a drink with him."

According to a Conservative backbencher, May is fundamentally unknowable, not given to easy chatter or shared confidences. She can be aloof, the backbencher says, and difficult to get close to, which might stand in the way of any potential leadership bid. He jokes that May can appear a bit like Karla, the inscrutable Soviet spymaster in John le Carre's novels.

"She's sphinx-like… I played a game with her once, which was trying to out-silence her in a meeting. She'll give nothing away. She'll sit there in silence. It's a good technique, used by interrogators, but I don't think it gets you very far. You don't feel you're having a conversation."

Others point out that her apparent distance is the result of an innate shyness and caution. She is a private person in an over-sharing age. "I suppose I'm not naturally over-effusive in wanting to go out there and tell everybody my story," May said in an interview with Total Politics magazine two years ago. "Showing that you can do something, that you're in the job and doing it, is more important than the back-story."

Such reticence means that there is precious little personal information about her in the public domain. The only child of Reverend Hubert Brasier, a Church of England vicar, and his wife, Zaidee, she grew up in Oxfordshire and gained a place at a grammar school that became a comprehensive. She read geography at St Hugh's College, Oxford, where she met her future husband, Philip, a banker she married in 1980. The couple have no children, which is said to have been a source of sadness and something she does not like to talk about in interviews.

But if you ask anyone who knows her for an entertaining anecdote or two, their faces turn blank, then mildly apologetic. "She likes to drink a St Clements [orange juice mixed with lemonade]," says Olsen, desperately trying to come up with something. "And she never swears."

"She stores her shoes in seethrough plastic boxes," says a colleague, furrowing their brow.

"If you were to ask me for an anecdote, I'd find it hard to think of one," says a Tory source. "Except that she can be a bit annoying."

I'm told she likes cooking, Alpine walking and refuses to buy food online because she enjoys pushing her trolley through the Twyford Waitrose in her Berkshire constituency. She adores cricket and one of her heroes is, somewhat improbably, Geoffrey Boycott. Other than that, she is adamant she has no role models.

Questions about her sense of humour tend to elicit a diplomatic pause. "Theresa and I used to love watching The Goodies," says a university friend. "That was our sense of humour." "She doesn't have a natural streak of piss-taking," admits Olsen, "she's too serious-minded for that. If you tell a funny story, she'll laugh but she doesn't tell stories herself."

On a work trip to the US some years ago, Fiona Cunningham tried to get her to say the popular street-talk phrase "Oh no you didn't" in an American accent, accompanied by the necessary finger-pointing and head-twitching. May was game enough to try but never quite loosened up enough to manage it.

"She's very proper," says someone who has worked closely with her. "I suppose she's quite guarded."

May does not give her trust easily but once she does, she is said to be tremendously loyal and inspiring of loyalty in others. There is a softer side to her that comes out when she is relaxed. Olsen recalls her being warm and kind to his toddler son, Lawrence: "He was crawling around her house, pulling out books, and she didn't care." At dinner parties, she often makes a beeline for other women and is genuinely interested in their lives. If one of her closest team of advisers is unwell or undergoing personal difficulties, May will check up on them with regular phone calls and texts.

"She is like a tigress looking after her litter," says one. "That's nice to know and it makes you want to work harder… She respects competence. She respects when people are willing to work hard – not just talking the talk, but walking the walk… She's got exacting standards, don't get me wrong. Unless you have those standards, maybe you find it hard working for her."

In fact, she once got so frustrated by a civil servant's inability to answer a direct question, she banged her head on the table. On another occasion, she is said to have physically taken a Number 10 official by the lapels of his jacket and removed him from the Home Office. She is, then, extremely dedicated to the job, sometimes still poring over her red boxes at 2am. She has been known to reply to emails on Christmas Eve. When May was diagnosed with Type 1 diabetes two years ago, the initial shock ("She was someone who never got ill," says an aide, "so she was quite upset because it made her feel vulnerable") was rapidly replaced by her customary pragmatism.

The workload at the Home Office is intense and comes with a threat to personal security from extremists. When she was first appointed to the job, a parliamentary colleague who has known May for more than a decade remembers asking her how it was going. "She looked at me and said, 'The stuff that goes across your desk…' and I could see, etched across her face, how overwhelming the role was from the outside, the risk that has to be borne."

Another MP says that when he recently had a meeting with May "she came across as almost fragile. She's quite a delicate woman. She's tall, her shoulders were sort of rounded. She was probably feeling a bit frazzled".

If that were true, it is possibly as a result of May's determination to be on top of her brief. "She's such a details person, she does actually read every submission back to front," says a former colleague. "Nothing slips through. I've had civil servants say, 'She knows more than I do.'"

And yet her critics insist she is more of a proficient corporate manager than an intellectually feisty creative thinker or innovator. She is, they say, simply not very exciting. "If she does have a broader vision," says a Tory source, "I don't know what it is."

Theresa May was 12 when she decided to be a politician. Growing up in an Oxfordshire vicarage, she became used to seeing her father working with people in the community, speaking to them, listening to his congregation and offering help when it was needed. The family talked about current affairs at the dinner table. It was, she later remarked, "a natural environment to seek a political future". As a child, altruism was encouraged – "You didn't think about yourself," she said in 2012. "The emphasis was on others." She had no siblings, which might explain both her shyness and her self-reliance.

A friend says her decision to pursue a political future was "a calling, a vocation… she doesn't think of it as work", and she remains a woman of faith. When she went up to St Hugh's College, Oxford, in 1974, a contemporary recalls her attending church on Sundays. "It was quite high church stuff – there was nothing evangelical about Theresa, ever. It was good, solid religion."

She met Philip, who was a couple of years below her, at a student Conservative Association disco, where the couple were introduced by Benazir Bhutto, the future leader of Pakistan, who was assassinated in 2007. The two of them bonded over a shared love of cricket – Theresa was known to have a soft spot for the West Indian fast bowler Tony Gray.

"Phil was a lot of fun," says a friend. "He had loads of levity – but she did too. It's a myth she wasn't jolly because she was. She was good fun. She would come up with witticisms and quips. She would make jokes – a lot of them were cricketing jokes, to be fair."

In tutorials, May was "very determined and diligent – you know, she did what it said on the tin. She would do the work while I got drunk". St Hugh's was still a women's college at the time but the university as a whole remained overwhelmingly male. "We weren't girly," says May's contemporary. "If you got into Oxford as a woman back then, you had a certain inner strength."

The same friend remembers May expressing admiration for Margaret Thatcher, who was then leader of the opposition: "I think the admiration was for what Thatcher was doing as a woman rather than her politics… I knew Theresa was interested in politics but there were no intimations back then that she would end up where she has. Did I think it was obvious she was going to become home secretary? No."

It was as a public speaker that May came into her own. She made frequent appearances at the Union but was also an active member of the Edmund Burke Society, an irreverent group that saw itself as the pretension-pricking antidote to the seriousness of university debating. The society would hold its debates on Sunday nights, in the Morris Room at the Union, accompanied by unlimited amounts of port, drunk from tiny glasses. Her peers included Michael Crick, the BBC journalist, and Damian Green, who until the recent reshuffle worked alongside May at the Home Office as police and criminal justice minister .

In the third term of her finals year, May took on the presidency of the Edmund Burke Society and came up with a series of lighthearted motions for debate, including "That this House thanks Heaven for little girls", "That this House would" and "That Life's too short for chess".

She would preside over proceedings with aplomb, brandishing a meat tenderiser as a gavel.

"She was very, very well-liked," says a friend. "I think part of the reason she never stood for election at the [Oxford] Union was that she wasn't a machinating politician. She wasn't somebody who would curry the support of different sides… She wasn't factional."

Even when she had graduated from Oxford and gone straight into a job at the Bank of England, May would return regularly to see Philip and would sometimes find herself roped into speaking, most notably opposing the motion in June 1978 "That sex is good… but success is better" in a debate organised by her boyfriend. (There is no record of whether her impassioned defence of the sexual act resulted in the motion's defeat or not.)

Perhaps the darkest period of her life came after the sudden death of her father in a car accident in 1981, four years after graduating. Her mother died a year later. Profoundly private and protective of her innermost emotions, May has refused to dwell on this painful loss in interviews. Olsen remembers her mentioning it to him only once, over a pint in a pub on a break from campaigning. "It was clear she loved her father very much," he says. May revealed no more. She takes the view that her personal feelings are not for public probing: the important thing is to get on with life.

And get on she did. After leaving the Bank of England in 1985, she was a financial consultant and senior adviser on international affairs at the Association for Payment Clearing Services. In 1986, she became a councillor in the London borough of Merton. Six years later, she stood in the general election and lost in the safe Labour seat of North West Durham. In 1997, she was elected MP for Maidenhead and joined William Hague's frontbench opposition team.

Her friends pay tribute to her husband for being a constant, supportive presence. Some talk about him in the same breath as Denis Thatcher, another stalwart husband who was prepared to stay out of the limelight while his wife got on with the business of running the country.

"Philip is really lovely," says a friend. "He's just a regular, nice guy who's bright like she is. They still totally love each other and have a great friendship. He is good for her because he's aware she's home secretary but she's still just Theresa to him. They are not one of those couples where one of them is a big name and the other one quite likes it [the reflected glory]. That would never even come into his mind… When they're together, they seem younger."

Could Theresa May be a future leader – possibly even our second female prime minister? Opinion remains divided. Even her supporters acknowledge that she is "more admired than liked" and that it might be hard for her to garner enough support from her fellow MPs to get through the first stage of selection. In recent weeks, she has been spotted in the parliamentary tearooms, meeting a select handful of politicians and sounding them out.

"She never used to do that sort of outreach," says a Conservative source. "She's not friends with anyone."

But there is an argument that admiration serves an ambitious politician better than likability. If you are well-liked by some, the chances are you are hated by others. If you are too concerned with making friends, you forget to worry about your enemies. Theresa May has never wanted to join the club. Her best chance for success might be staying out of it.