The new director general of MI5, Eliza Manningham-Buller, takes up her post on Monday.

She replaces Sir Stephen Lander who left last week after six years in charge.

Ms Manningham-Buller, 54, was his deputy for five years and joined the security service in 1974.

She is understood to be keen to widen the range of recruits appointed to the security service to include more from ethnic minority groups.

Ms Manningham-Buller worked in the Cold War

Her specialist field is counter-terrorism, which is especially relevant given the threat posed by Islamic groups linked to al-Qaeda.

MI5 has been criticised for failing to penetrate such groups.

The day after the 11 September attacks, Ms Manningham-Buller flew out to Washington to liaise with the US authorities.

MI5, which was founded in 1909, has embarked on a campaign to recruit more widely, as only four per cent of staff are black and Asian at the moment.

Efforts will also be stepped up to to increase the number of candidates from outside Oxford or Cambridge universities.

Ms Manningham-Buller is said to be more extrovert than her predecessor.

But Whitehall sources say she will maintain a low profile, with no press conference on her first day, few public appearances and - unlike the first woman head of MI5, Dame Stella Rimington - no memoirs.