Tony Blair was often criticised for his laid-back "sofa" style of Government, taking decisions among close aides in his den at No 10.

If Gordon Brown takes over, Downing Street could be more like Dragon's Den, the TV show where would-be entrepreneurs are ruthlessly grilled by successful businessmen.

Mr Brown rattles off his opinions with his characteristic machine gun delivery and has a reputation for not suffering fools gladly.

Where Mr Blair could charm and persuade, sometimes taking self-deprecation to an art form, Mr Brown delivers his opinions with cast-iron certainty and takes their assumptions for granted.

He has partly acknowledged this, promising a more collegiate, listening style of government. But after 10 years of pulling the levers of power at the Treasury, where actions always equal outcomes, old habits may prove hard to shake off.

The Chancellor famously likes watching football on TV with pals, sharing cans of beer, and his interest in the game is genuine.

On a recent visit to Afghanistan he chatted knowledgeably to a squaddie who was a Leeds United fan, commiserating with him on his club's decline.

He has always been more relaxed and forthcoming in private, even with journalists, than his dour public persona might suggest.

He will cheerfully regale his audience with anecdotes and his thoughts on anything from Scottish nationalism to Martin Luther King.

But the man once famously described, allegedly by friends of Tony Blair, as "psychologically flawed" has also been the subject of scathing comments from ex-Cabinet colleagues and the former top civil servant at the Treasury, Lord Turnbull.

In comments to the Financial Times he said of Mr Brown's relationship with colleagues: "He cannot allow them any serious discussion about priorities. His view is that it is just not worth it and 'they will get what I decide'. And that is a very insulting process."

He said this strategy had enhanced Treasury control but had come "at the expense of any Government cohesion and any assessment of strategy".

Lord Turnbull added: "You can choose whether you are impressed or depressed by that, but you cannot help admire the sheer Stalinist ruthlessness of it all."

And ex-Home Secretary Charles Clarke said recently Mr Brown must "prove his fitness" to be Prime Minister. "Part of the problem is that he lacks confidence. He is nervous," he said. "That could all change when the burden of waiting for the job is lifted from his shoulders and I think it probably will. But the problem is, nobody really knows." Visitors to No 10 have often left after meeting Tony Blair with the impression he had cheerfully agreed with them, until they realised they could not quite remember exactly what he had so smilingly said. Few have left meetings with Gordon Brown under any illusions about his opinions. David Blunkett recalled in his diaries that he once got so angry during a meeting involving the Chancellor that he snapped a pen in half and threw it across a table. Will the public image of the Iron Chancellor change in No 10? Mr Brown seems to have made some effort to brush up his physical appearance, with more slickly coiffured hair and having famously had his teeth done. But he has so far showed little of the flair for style and presentation that were the hallmarks of Mr Blair's early years in Downing Street. The Chancellor would probably regard concern for such matters as frippery. He may yet change his mind when he discovers just how harsh the glare of the spotlight on a Prime Minister's every move is.