LONDON, June 16 Britain's prime spy agency, the MI6 currently very active in Afghanistan and Pakistan is to have a career diplomat as its new chief, a first-time break from the tradition of internal promotions.

A 10 Downing announcement on Tuesday said Sir John Sawers, the UK ambassador to the UN, will take over as the new chief in November when the MI6 will be celebrating the 100th year of its founding.

It is highly unusual for a diplomat, or any outsider, to be appointed as the head - or C for chief, as he is still officially called - of MI6.

Charles Farr, head of the Office of Security and Counter-Terrorism at the Home Office, had been among those tipped to take over from the outgoing chief , Sir John Scarlett who after having survived as the chairman of the joint intelligence committee the controversy over the Blair government's Iraq weapons' sexed up' dossier was elevated to the top job in 2004.

Sawers, 53, is a diplomat who has been close to Downing Street and the foreign policy establishment for many years.

He has been the political director at the Foreign Office, the ambassador to Cairo, and Britain's special representative in Baghdad.

Between 1999 and 2001, he was the foreign affairs adviser to Tony Blair, covering a period that included the Kosovo war.

He also contributed to negotiations on Northern Ireland and the implementation of the Good Friday agreement.

According to The Guardian, Sawers is known to adopt a hard line on Iran and be sceptical about any suggestions that it does not want to build nuclear weapons.

Traditionally, the head of MI6 signs letters and memos “C”, written in green ink. His signed documents are sent to the Queen as well as to government departments.

Sawers will be taking on the top MI6 post at a time when, after being severely cut at the end of the cold war, the agency is expanding fast and attempting to attract people from a wider variety of backgrounds.