Steve Hilton: The unseen author of David Cameron's bid for No 10

As the applause rang round the conference hall after David Cameron's strongest speech as Tory leader, the author was in his usual place firmly behind the scenes.

Steve Hilton is a pint-size Rasputin whose influence is as large as his profile is low. He loathes the limelight, never gives interviews, and is sighted at Tory conferences about as fleetingly as members of the Revolutionary Communist Party.

He rarely goes to any of the dozens of parties in the conference hotel because he is a driven workaholic who is either working on the leader's speech or working on some of the other announcements.

While he may not be seen, his presence is everywhere from the conference slogan, Plan for Change, to the conference literature. As important to Mr Cameron as Alastair Campbell and Peter Mandelson were to Tony Blair, he prefers it that his name, which does not appear on the Conservative website, is not known outside the Westminster glasshouse.

He does not even have an official job title but he does have a large salary, around £180,000, which is not bad for someone who moved to California with his new wife and child this year.

Yet Mr Hilton earns the money because he is credited with changing Mr Cameron from pinstriped Old Etonian "Tory boy" into a modern, bicycling, supercool Dave, who buys his suits at Marks & Spencer, hugs hoodies on council estates and huskies on Norwegian glaciers. Mr Hilton has not worn a suit and tie for more than a decade.

It was Mr Hilton who insisted that before they devised new policies they first had to decontaminate the Conservative brand. The rebranding part of the operation complete, with the Tories way ahead in the polls, Mr Cameron was finally allowed to flesh out in his speech a series of core Conservative principles which even included subjects once deemed by Mr Hilton as taboo, such as Europe, with his referendum pledge on the Lisbon Treaty. Mr Hilton took the lead in the speech writing process.

With the exception of William Hague, the shadow foreign secretary, and George Osborne, the shadow chancellor, Mr Hilton, 39, has more clout than the entire shadow cabinet put together. He has been behind every projection of Cameron from the open-neck shirts to the trip to Rwanda.

They became friends when they worked together at Conservative Central Office during the unexpected victory over Labour in the 1992 election. Mr Hilton, a bright young thing at Saatchi & Saatchi, returned to the advertising agency after the election.

Maurice Saatchi, the founder of the agency, has said: "No one reminds me as much of me when young as Steve." He left to set up his own consultancy, Good Business, advising companies on how they can do good – not least for their own images – by being socially responsible.

His clients included McDonald's and Coca-Cola and, if you are in any doubt about the Cameron philosophy, the Good Business website offered discussion topics such as, How can we get brand benefit from social programmes without being – and looking – superficial?

He returned to the political arena in 1997 as one of the architects of the notorious "demon eyes" poster campaign about Tony Blair, which backfired on the Conservatives.

At the 2001 election, appalled by the drift to the Right under William Hague and the inevitable scale of the Conservative defeat, he voted Green for the first time.

By the time Mr Cameron became leader four years later (Mr Hilton was one of the first to urge him to run), after a third successive electoral defeat, the two close friends had decided that green issues were the cleverest way to demonstrate the party had changed.

Mr Hilton's position in the Tory Party hierarchy was underlined when he began dating Rachel Whetstone, who had been Michael Howard's communications chief.

Earlier this year, they married and had their son Ben christened on the same day. They moved to a big house in Paolo Alto, California, when she became a vice-president of Google. Friends for years before they married, they are godparents to Mr Cameron's son, Ivan.

Despite the thousands of miles of separation, and six hour time difference, Mr Hilton insists he is still plugged in to project Cameron. He takes part in the daily 4pm meeting in a conference telephone call from his home. He comes to Britain every four weeks for seven days at a time. He remains one of the true political heavyweights in the Cameron kitchen cabinet, in more ways than one these days.

The shaven headed Mr Hilton, a teetotaller, used to worked off his immense nervous energy with long sessions in the gym each day. With his finely honed physique, and dressed in his trademark skin tight black T-shirts and jeans, he would not have looked out of place on the dance floor in a gay nightclub.

In truth, it would no longer be fair to call him pint size. Having moved to the United States, the land of the free and the home of the beefburger, he has a new baby son, no time for the gym, has given up smoking, and his weight has ballooned by at least two stone.

He is the son of Hungarian refugees called Hircksac, who fled their home during the Hungarian Revolution of 1956 and anglicised their name to Hilton when they settled in Britain. They took their name from the first hotel in which they stayed.

The family lived in relative poverty, unlike most of Mr Cameron's main advisers. He went to Christ's Hospital in Sussex, a private school where children from less fortunate families have nearly all their fees paid by a charitable trust, before reading Philosophy, Politics, and Economics at Oxford.

He continues to devour political philosophy none more so than Philip Gould's The Unfinished Revolution, which was an insider's account of New Labour's return to power by Tony Blair's pollster. It is as essential reading to Mr Hilton, as were the free market treatise of Hayek and Adam Smith to the early Thatcherites.

Before the last election he tried to win selection for the safe Tory seat of Surrey Heath, but was beaten by another member of the Cameron cabal, Michael Gove, the highflying shadow schools secretary.

Mr Hilton is now more than happy to remain a shadowy figure behind the seat of power where he will remain right up until the next general election.

If, as they confidently expect, Mr Cameron wins, Steve Hilton is expected to return to Britain with his wife to bring up their son here.

He will be able to write his own job description at Downing Street – as long as he is not required to wear a suit and tie.

CV

Name: Steven Hilton

Date of birth: Aug 25, 1969

Family: married to Rachel Whetstone, former mouthpiece for Michael Howard. One of the most powerful women at Google. One son, Ben

What they say about him: David Cameron, criticised for taking £11,000 from a biographer – which he gave to charity: "I will be hiving off a little bit to buy Steve Hilton a suit."

What he says about himself: "Nothing in case it gets reported by the newspapers."