I'm standing in the garden of the Excelsior Hotel, a vast Moorish confection that sits astride the Venice Lido. In front of me are members of the late Stanley Kubrick's extended family: behind me, a gaggle of super-senior Warner Bros executives.

This is a very special, private moment. Soon, the eight black-clad usherettes who led us into the garden will herd us out of it, like gorgeously mute sheep-dogs, into the madness beyond. We will parade between two lines of steel barricades, holding back the frantic fans, paparazzi and TV crews awaiting the stars of the Venice Film Festival.

First, we must wait for Tom Cruise and Nicole Kidman. The festival's opening film is Kubrick's swansong Eyes Wide Shut, and its stars are gracing us with their presence. The movie has done less than stellar box-office in the US: a gross of $60 million for a flick in which Tom stars and Nicole gets her kit off is distinctly disappointing.

Still, the couple are unswerving in their promotional efforts - Venice is the first leg of a three-day party that will move to Paris and London on successive nights - and their own allure is bomb-proof. The hysteria surrounding them in Venice is so intense that when they go for a trip around the lagoon, an Italian man in a smart black suit runs down the jetty and dives into the water, frantically paddling after their departing water-taxi. When heaved back on to dry land and asked why he had done it, he splutters, 'Because I love-a Nicole!'

Back in the garden, many minutes pass, many mobile phones are consulted. Then there is a sudden bustle of bodyguards and a gleam of perfect teeth. They're here! Tom looks tan, trim, super-confident, his smile set to megawatt power. He is wearing a grey suit and an enormous pair of chunky black shoes. Does he have size 14 feet? Does he require extra elevation? I cannot say.

Next to him, Nicole is impossibly, translucently slender, tentative, even vulnerable next to her super-confident husband. Her silken dress is palest violet. Her skin is gleaming white.

Around me, hardened movie pros gawp like drooling teenyboppers. Terry Semel, a Hollywood power-player who was in charge of Warners when Cruise was still Thomas Mapother IV, bursts into applause. I, too, am awestruck. I have gazed upon Their Majesties. If the cuttings are to be believed, this is a mighty privilege. Extras on Eyes Wide Shut were said to have had to sign contracts forbidding them even to look at Cruise. Yet I have been admitted into his presence. And I have done so by saying four magic words: 'I'm with Jocelyn Pook.'

Ms Pook composed all the original music for Eyes Wide Shut. Previous Kubrick films were scored by his daughter Vivian using a pseudonym. Many film buffs assumed it had happened again. 'It does sound like a made-up name,' says Pook. But it isn't.

Now, like the lone Brit to make it to the second week of Wimbledon, Pook is Our Lass at Tom and Nic's bash. She's been accepted into the Kubrick/Warner family. Last night, she dined with the clan, plus Nicole. It was a touching reconciliation because, as she ruefully confesses, 'I'm a bit of a black sheep at the moment.'

Before Eyes Wide Shut opened, Pook told a reporter that she had scored its orgy scene, not knowing that Kubrick was manically secretive about his films' contents. 'In hours it was all over the Internet. I got rung up by Warners: "What are you doing? No one knows about the orgy!" '

It then emerged that the orgy score contained a vocal chant, taken from a sacred Hindu text. Not surprisingly, American Hindus objected, so the score was re-recorded and the film re-printed, at considerable cost. It could have been worse: Pook's first choice was a reading from the Koran.

A Guildhall graduate, she has spent most of her career at the indie end of rock, first as a Communard, then as a string arranger for acts such as Elvis Costello and Massive Attack. When Kubrick first called, she was so ignorant of his status that she put him on hold while she finished talking to a friend. Only with time did she learn the thrill to be derived from the words, 'Hang on, I've got Stanley Kubrick on the other line.'

'I'm learning as I go along,' Pook says, sipping Tokai, casting an eye over Venice, and tucking into an expenses-paid lunch on the roof-terrace of the Danieli Hotel like a proper pro. At the LA première, she recalls, the cinema was so freezing, she had to put on something over her sleeveless frock. All she had was an old blue cardigan. She did not realise that her name would be called out and she'd have to stand to take a bow.

'Spielberg, Scorsese and Sydney Pollack were sitting just in front of me, and I was standing there, desperately trying to undo my cardie.'

In Venice, she faces the audience in an immaculate black dress, with not a woolly in sight. Tom and Nicole, enthroned in the centre of the front-row circle, graciously applaud their handmaiden's efforts. I am down in the stalls, with the masses. Just in front of me sits Fergie. I am close enough to see the sweat stains in the armpits of her sleeveless olive silk dress and watch the relentless mastication as she chomps on her chewing-gum.

The duchess was royal. Tom and Nicole still are. Cruise works his fans like a blend of Prince Charles and President Clinton. Nicole is as gracious as Diana. As with many regal occasions, there is a mass of tedious ceremonial. A full hour of speeches - the power of cinema, the genius of Kubrick, the wonders of Venice, etc - climaxes when an on-stage panel slides to one side and there, magically whisked from their seats, stand Mr and Mrs Cruise.

They submit to a question-and-answer session translated by an interpreter with the unfortunate habit of interrupting Cruise and then forgetting the last half of his quotes.

Finally, Tom tires of the charade. Beaming that smile, but brooking no contradiction, he tells the audience: 'You don't want to hear me talk. You want to see the movie.' We certainly do. But at the credits the applause is polite, rather than wild. Are Tom and Nicole flogging a sick horse? That makes them even more like royalty.