Cameron already knows his lines – but are they good enough?

Andy McSmith reveals the meticulous method behind Tory leader's speech-making

One thing David Cameron will not be doing this morning is rising early to work on his conference speech. It is all done. He has been going through it so often he knows it virtually by heart. There will be no more changes now unless a major event dominating the morning's news requires a comment.

There is no bigger event in an opposition leader's calendar than the set-piece speech to his party's annual conference. Today's will be the most testing that Mr Cameron has had to deliver since he was on the rostrum in Blackpool four years ago, contesting a closely fought leadership election.

That speech was the making of David Cameron, and the destruction of his rival David Davis's hopes of leading the Conservatives. Mr Davis entered the race as the frontrunner, but too many people had a hand in his conference speech, which was a rambling peroration that had eyes glazing over in the hall. Mr Cameron was the untested outsider, but one masterly speech, delivered from memory, without notes, put him out in front.

The lesson that Mr Cameron absorbed is not to allow too many people to get their hands on a big speech, stuffing it with their pet policies, but to rely on a tight circle of people whose professionalism he can trust, and to have the speech ready to go before the day on which it is delivered.

The last Tory leader but one, Iain Duncan Smith, was so nervous about his last conference speech that he kept altering it, even in the final minutes before he was due on stage. As he started speaking, an aide backstage was frantically retyping the script as it rolled through the autocue. The speech was a turkey. Mr Duncan Smith was ousted soon after. Mr Cameron is not going to make that mistake.

There are really only two minds behind today's address: his own, and that of Steve Hilton, the marketing guru who was the brains behind Mr Cameron's branding of the Conservatives. Though Mr Hilton moved to California last year, where his wife, Rachel Whetstone, is a vice president of Google, he came back a month ago to return full-time to Cameron's office.

Work on the speech began about three weeks ago. The first meeting involved a handful of people, including Mr Cameron himself, Mr Hilton, and his main speechwriter, Ameet Gill.

Mr Cameron wanted this speech to stick to broad themes, giving people reasons to trust the Conservatives. It should give them hope. It should tell the electorate what sort of prime minister David Cameron aspires to be, rather than make a series of announcements on what the party would do. After the first draft was drawn up, the circle of people involved widened, taking in Mr Cameron's chief of staff, Ed Llewellyn, his deputy, Catherine Fall, the communications director, Andy Coulson, and the shadow Chancellor, George Osborne.

One reason for seeking other opinions is to avoid basic mistakes – for instance by falling into Mr Davis's trap of trying to cover every possible subject. Conversely, nothing major must be left out, and the time allocated to each topic must be in proportion to its importance. Last week, Gordon Brown was criticised for devoting only 35 seconds of a 59-minute speech to the Afghan war. Yesterday, the spread betting firm Sporting Index was taking bets on whether Mr Cameron will allocate twice that length to the war.

The speech could not be completed until the Labour conference was over. Mr Hilton stayed up all night on Monday with the lights blazing in his hotel room, working on a definitive draft.

The final draft was presented to Mr Cameron, printed in 18-point type and double-spaced, so that he could underline in blue ink the passages that he wanted to emphasise, and make notes.

Mr Cameron does not usually read out his speeches. He likes to deliver them from memory or headline notes, walking about to give the occasion informality. But this speech is too serious for a walkabout, and will be delivered from a script. It is not a format that Mr Cameron likes, but the image of him standing still at the rostrum will, if it goes well, leave a lasting picture of man who is steady under pressure and knows what he wants to do.