One of the country’s most dedicated “Deadheads” – as fans of the rock band the Grateful Dead are known – is to become the Government’s top intelligence adviser.

Alex Allan, who is Permanent Secretary at the Ministry of Justice, is such an enthusiast for the Grateful Dead, who were a leading American “underground” band during the hippy era, that he places their music at the top of his list of interests, above sailing, cycling, computers and bridge.

Gordon Brown approved Mr Allan’s appointment yesterday as the next chairman of the Cabinet Office Joint Intelligence Committee (JIC), a full-time post that requires him to read all the most secret intelligence and to assess its value before providing a weekly summary for the Prime Minister and other appropriate Cabinet ministers in the so-called Red Book.

Harrow and Cambridge-educated, Mr Allan was selected from a shortlist of three candidates, and was recommended for the job by Sir Gus O’Donnell, the Cabinet Secretary. He will replace Sir Richard Mottram, who retires this week.

After the report by Lord Butler of Brockwell, the former Cabinet Secretary, into the faulty intelligence behind the Government’s dossier on Saddam Hussein’s weapons of mass destruction, Tony Blair, as Prime Minister, agreed that future heads of the JIC should be chosen not just for their ability but because the appointment would be the last in their career. The idea was to avoid any risk that a future JIC chairman could be accused of being too close to the Government in order to safeguard promotion prospects.

The chairman of the JIC who produced the dossier on Iraq’s weapons of mass destruction in September 2002, six months before British troops took part in the US-led invasion of Iraq, was Sir John Scarlett who went on to become head of MI6. Lord Butler said that Sir John was the right man for the job and recommended that his appointment should stand but considered it prudent that future JIC chairmen should be approaching the end of their careers.

Mr Allan, 56, is one of Whitehall’s more colourful characters. During a 1980s train strike he went to work on a windsurfer up the Thames, complete with pinstripe suit, bowler hat, brief-case and brolly. He came a cropper, ending up in the river, and there are photographs on his personal website to prove it.

When he takes up his new appointment, he will serve solely as JIC chairman, unlike the man he is succeeding. Sir Richard carried out the twin roles of JIC chairman and Security and Intelligence Co-ordinator. Robert Hannigan, formerly of the Northern Ireland Office, has been given the other intelligence appointment.

Mr Allan has a Civil Service and Diplomatic Service background. He was High Commissioner in Australia between 1997 and 1999 and was Principal Private Secretary to John Major when he was Prime Minister. He spent most of his early Civil Service life in the Treasury, serving as Principal Private Secretary to Nigel Lawson when he was Chancellor. He also worked at Customs & Excise. A few years ago he took a break from government service to live in Western Australia.

Mr Allan, who is married, was Permanent Secretary at the Department for Constitutional Affairs from 2004 until it merged with the National Offender Management Service this year to create the Ministry of Justice.

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