Mussa Kussa in his last public engagement for the Libyan regime announcing a ceasefire on March 11

Libyan leader Muammar Al Qathafi has been dealt a severe setback with the defection of one of his most trusted allies, Foreign Secretary (Minister) Mussa Kussa who arrived in Britain of his own free will Wednesday evening saying he was was resigning his post and was "no longer willing" to represent the Libyan regime.

The UK Foreign and Commonwealth Office confirmed that 61-year-old Mussa Kussa had travelled to Britain and said he had arrived on a plane from Tunisia saying he no longer wished to represent Al Qathafi on the world stage. "We can confirm that Mussa Kussa arrived at Farnborough airport on March 30 from Tunisia," a spokesman for the Foreign Ministry said.

The spokesman went on to say: "He travelled here under his own free will. He has told us that he is resigning his post. We are discussing this with him and we will release further detail in due course.

"Mussa Kussa is one of the most senior figures in Al Qathafi's government and his role was to represent the regime internationally - something that he is no longer willing to do.

"We encourage those around Al Qathafi to abandon him and embrace a better future for Libya that allows political transition and real reform that meets the aspirations of the Libyan people."

Questions had earlier been raised about Mr Kussa's whereabouts after Tunisian news agency TAP earlier in the week reported he had entered that country, but gave no reasons for his move.

A Libyan government spokesman later claimed Mussa had not defected but was merely on a "diplomatic mission". He however but declined to say where he was going. Libya's deputy foreign minister Khalid Kaim dismissed the reports as "nonsense".

Within hours the Foreign Office confirmed Mussa Kussa, who served in the Libyan government as Minister of Foreign Affairs from March 2009, into the 2011 Libyan uprising, until resigning March 30, was seeking refuge and encouraging further regime defections.

Previously, for 15 years, from 1994 to 2009, Kussa headed the Libyan intelligence agency and was considered one of the country's most powerful figures.

Talking to Sky News Noman Benotman, a Libyan-born friend of Mr Kussa and analyst at Britain's Quilliam think-tank, described Kussa's defection as " an absolutely massive loss for Al Qathafi." He went on to say that Mr Kussa wasn't happy at all. He doesn't support the government attacks on civilians."

Mussa Kussa has long been regarded as one of the Libyan regime's best diplomats and very close to Muammar Al Qathafi. He attended American Michigan State University, and earned a bachelor's in sociology in 1978.

Kussa worked as a security specialist for Libyan embassies in Europe before being appointed as Libya's Ambassador to the United Kingdom in 1980 from where he was expelled after stating in an interview with The Times newspaper that his government intended to eliminate two political opponents of the Libyan government, who were living in the UK.

Later, from 1992 until 1994 he served as Deputy Minister of Foreign Affairs and also headed the Libyan intelligence agency from 1994 to 2009.

Mussa Kussa was regarded as a key figure in the normalisation of relations between Libya and many NATO nations, including the United States and the United Kingdom.

He was also reported to have been key in securing the release of convicted Lockerbie bomber Abdelbaset Ali Mohmed al-Megrahi. In a second visit to Britain in January 2009, he was listed as Minister of Security

On March 4, 2009, Kussa was designated as Minister of Foreign Affairs, replacing Abdel Rahman Shalgham, in a ministerial reshuffle, and a month later presided over the 28th council meeting of the Arab Maghreb Union (comprising Algeria, Libya, Morocco, Mauritania and Tunisia) in the Libyan capital Tripoli.

His last official public engagement on behalf of the Libyan regime was on March 11 when, "hands shaking" he announced a ceasefire weeks into the 2011 uprising, after the UN Security Council had opened the way to a no-fly zone.

Sources close to him reportedly said that he was shaken and very disappointed when, despite the ceasefire announcement he was made to look unreliable to the Western world when the Al Qathafi regime went back on its word and “duped” the world into making believe that he was to stop the attacks on civilians but then went back on his word and kept up the barrage.

Kussa's last commitment as a member of the Libyan regime was on March 29 when he wrote to United Nations Secretary General Ban Ki Moon, nominating the former foreign minister of Nicaragua’s socialist Sandinista government and one-time president of the United Nations General Assembly, Miguel d’Escoto Brockmann, as Libya’s new ambassador to the UN.

A day earlier, however, Mr Kussa had departed Tripoli by car for the Tunisian capital, Tunis, via the Ras Ejder border crossing. At the time, a Tunisian Government spokesman via Tunis Afrique Presse stated that Kussa had arrived on a "private visit."

He departed from Djerba on a Swiss-registered private jet, Wednesday and arrived at Farnborough Airfield, England later in the day, according to Libyan sources on a diplomatic mission.

Instead, according to an official press statement by the UK's Foreign and Commonwealth Office Mussa defected and, unhappy with Libyan Army attacks on civilians he no longer wished to represent the Libyan government, putting more diplomatic stress on the structures of state of the Al Qathafi regime.

Middle East expert Shashank Joshi said: "The latest Arab state to increase the pressure on the Gaddafi regime is Tunisia, whose prime minister announced plans to freeze all assets belonging to the Libyan leader."