The cause took on a more militant aspect in the early 1900s with the formation of the Women's Social & Political Union and the activities of the Pankhursts which frequently led to imprisonment and even force-feeding of hunger-striking suffragettes.

The onset of the First World War led to a "truce" to concentrate on the war effort, in which women were heavily involved.

After the war, an electoral reform conference recommended a limited measure of women's enfranchisement.

In 1918, women over 30 were given the right to vote, quickly followed by the passage of a law enabling women to be eligible for election as Members of Parliament at the younger age of 21.

But only 17 out of 1,623 candidates at the subsequent general election were women.

Christabel Pankhurst polled the most votes at the election but failed to gain a seat: the only woman to be elected, Constance Markievicz, did not campaign and, as a Sinn Fein member, never took her seat.

The first woman to do so was Nancy, Lady Astor, elected for the Sutton division of Plymouth at a by-election in 1919. She made her maiden speech in February of the following year and, in 1923, piloted the first ever bill sponsored by a woman onto the statute book.

The first woman minister was Margaret Bonfield in 1924 (Ramsey MacDonald's Labour government); she became a cabinet minister in 1929. Voting age for women was reduced in 1928 to 21 (the same as for men).

It was not until after the Second World War that another milestone was reached - the first woman was nominated at the beginning of the 1946-7 session to the Chairman's Panel which allowed her to preside over a debate of the whole House in committee, which she did on 31 May 1948.

The first woman to occupy the Speaker's chair was Betty Harvie Anderson (Conservative), appointed deputy chairman of the Ways and Means committee (a deputy speaker) in July 1970, taking the chair later that day during the Queen's Speech debate when she was addressed as 'Mr Deputy Speaker'.

The first woman Speaker, Betty Boothroyd (Labour) was chosen in 1992 (in the first contested election since 1951). She had been a Deputy Speaker since 1987.

Margaret Thatcher was, of course, the first female prime minister - from 1979 until her resignation in 1990, having been elected Conservative party leader in 1975, deposing Edward Heath.

She holds the record for the longest serving twentieth century prime minister - eleven and a half years.

Ironically, Mrs Thatcher's election to the premiership brought with it the lowest tally of female MPs (19) since 1951.

This situation was reversed by the general election of May 1997, when a particularly large number of women MPs were elected to the Labour benches (101).

In all 120 women were elected to Parliament in 1997.