Will the honeymoon last?

Gordon Brown's son, John, has a new catchphrase - "Smile, Daddy". The prime minister does not need much prompting these days. There may have been warm white wine rather than champagne at the party after he was confirmed as the next Labour leader but those who know him well say that he is a changed man.

Friends say that the dour Presbyterian Scot is lightening up — he is planning to wear white tie, not a lounge suit, to state banquets. David Blunkett, the former home secretary, says: "This is the first time Gordon's been lucky, just as he takes centre stage David Cameron and his Tory party implodes."

Sarah Brown "looks ten years younger", says one friend. "From the day Gordon realised there would be no other contenders for his crown she began laughing again. It has been a tough few years for her, first with Jennifer and then her new baby. Now she has finally got her honeymoon and she is enjoying every moment."

But will the honeymoon last? Will Brown be quite as sunny when he is dealing with military crises, Cabinet revolts and a weekly Prime Minister's Questions?

Gordon Brown has lived in the shadow of Tony Blair for so long that it is hard to know whether he will wilt or flourish.

Some ministers and civil servants still wonder whether he has the human touch. Alastair Campbell may have edited the negative references to the Chancellor out of his diaries but there is no shortage of people who are willing to list his "psychological flaws".

Even Brown's closest friends admit he has a furious temper. "He will shout and scream — but after a few days he calms down," says one. His e-mails are written in angry capital letters and are full of spelling mistakes as he bashes the keyboard with two nail-bitten fingers.

Officials argue that Brown suffers from his reluctance to take advice. According to one senior figure, he was warned about the problems that tax credits were likely to create, but decided to press ahead with their introduction anyway.

Obstinate will

The most recent policy row came a few months ago over welfare reform: the banker David Freud, who had done a review was hauled into the Treasury to present his findings. "He came and said hello, got a 45-minute rant from Gordon then said goodbye," says a Whitehall source. "Then he was marched into a room full of advisers who shredded him. He was rather bruised that he'd been told specifically to come on his own."

It is said that he has not spoken to Jonathan Powell, Blair's chief of staff, for more than ten years. "Gordon has a weakness for people who have shown themselves willing to lay down their life for him," says a former civil servant.

Another official says: "It's hard to know what Gordon wants. He always leaves it to his adviser, Shriti Vadera, to explain his hand-waving. He surrounds himself with second-rate yes men, he doesn't want anyone who threatens his chain of command."

Brown is all too aware of criticisms made of him. "He knows how people want him to change and he's determined to do it," says a minister close to him. Recent speeches have stressed his intention to "listen" and to "learn". He intends to counter the control freak charge by stressing his commitment to devolving power.

On his first day as prime minister, he had planned to announce the creation of a constitutional convention, involving the public, to work out what should be included in a Bill of Rights.

On Iraq, he has made it clear there will be no immediate withdrawal. He will not produce a timetable for bringing troops out but he believes that wars should be handled differently in future. The next prime minister will combine a hard-line approach to terrorism with a softer approach to prisons: "tough on the causes of crime as well as tough on crime", as one aide puts it.

Left-wingers already scent betrayal. Vivienne Westwood, the fashion designer, says: "How can Gordon Brown have a moral compass? He's acquiesced in all the damage that Tony Blair has caused."

Fiona Millar, Alastair Campbell's partner and an education campaigner, says: "There's a danger that he disappoints everyone, people's expectations that he will be different are high." For Brown, the path to Downing Street has been a huge struggle. But it could be that the real battles are only about to begin. "It's rare to find such great strengths and huge weakness combined in the same person," says a former senior civil servant, "both are going to be tested to the limit."