Deputy to Sir Jonathan Evans is likely successor but will take up job amid evidence of MI5's role in secret rendition and torture
He cannot be named – in the unlikely event he fails to land the job – but the firm favourite to become the next head of MI5 is known to be a keen bird-watcher, it can be revealed.
Currently deputy to Sir Jonathan Evans, whose retirement next month was confirmed to MPs by Theresa May, the home secretary, on Monday, the likely successor has been responsible for handling counter-terrorist operations at the security agency.
But the anticipated internal succession has not yet been confirmed because other senior officials, including at least one not currently in MI5, have applied for the post. A final decision will be made by the home secretary, probably after consulting the prime minister.
Evans had told David Cameron and May earlier this year that he wanted to leave when his existing contract ran out in mid-April. Knighted in the last New Year honours list, Evans was also MI5's chief counter-terrorist officer before he took over from Lady Manningham-Buller in 2007.
In recent years he has had to defend the agency against evidence that, with MI6, and apparently with ministerial authority, it was complicit in the secret rendition, abuse and torture of UK citizens and residents detained by the US as terror suspects.
He was a driving force behind the justice and security bill, which will introduce secret court hearings and is designed to prevent sensitive information in the hands of the security and intelligence agencies from ever being disclosed. The bill will be the subject of crucial votes in the House of Lords (on Tuesday.
However, Evans expressed his concerns in an interview on BBC Radio 4 earlier this month when he said he had to warn new recruits to keep their activities "ethical", "legal" and "proportionate" to retain the trust of ministers and the public.
"One of the things I say always to new members of the service is that there may be a temptation to cut those corners but in the longer term that will be a real problem to us," he said.