Try digging around for information on Stephen Lander, the director-general of the Security Service, and there is precious little you will find.

Man at the top

A dark-haired, Cambridge-educated bureaucrat in his early 50s, Mr Lander took over the top job at MI5 in April 1996 when Dame Stella Rimington stepped down.

Jack Straw: Met with MI5 boss Stephen Landers

But whereas Dame Stella became a semi-public figure, her successor is best-known for his increasingly frequent carpetings by Home Secretary Jack Straw over embarrassing leaks by former agents and defectors.

Mr Lander met with Mr Straw this week over revelations by former KGB officer Vasili Mitrokhin, who provided MI5 with documents implicating Britain's "granny spy" Melita Norwood back in 1992 - yet she has never been charged for supplying the Soviets with nuclear secrets.

Saying little

The closest any profile-writer gets to describing Mr Lander is to mention that he is "discreet and quietly spoken".

Annie Machon, a former MI5 agent and girlfriend of disgruntled former spy David Shayler, pulled fewer punches when she said he "lacked presence and charm and belittled officers' work".

Far-reaching powers

In 1998, Mr Lander ranked 168 on the Daily Mail's list of the 300 most powerful people in Britain - just a couple of places ahead of Peter Stothard, editor of The Times, the newspaper serialising the book by former KGB officer Vasili Mitrokhin which unmasked Mrs Norwood.

He and his deputy, Eliza Manningham-Buller, are directly responsible for choosing between what the world at large may regard as legitimate targets for MI5 agents, and those who are not.

Low profile

Mr Lander would appear to be a suitably shadowy figure to head the agency once so secret that successive governments refused to acknowledge it existed.

Founded in 1909, MI5 - standing for the Military Intelligence section 5 - had the job of counter-espionage in both world wars, before targeting spies working for the former Soviet Union and its allies during the ensuing cold war.

It was 1989 before the government officially acknowledged MI5's existence.

Former MI5 head Dame Stella Rimington

Its budget had been hidden in the budgets of other government departments. And MI5's phone number and headquarters address were unlisted and until Dame Stella was appointed its first woman head in 1991, the identity of its chief was never officially revealed.

"MI5 does not kill people"

Although now on the Internet, MI5's Website is of little of interest to those seeking cloaks and daggers.

And its Myths and Misconceptions section contains denials of tailing the Royal Family, and says it "does not kill people or arrange their assassination".

Telephone-tapping is also denied, as is a plot to undermine the former Prime Minister Harold Wilson, which was claimed by former Security Service officer Peter Wright in his book Spycatcher.