Gwyneth Paltrow was happy to be snapped with co-star Robert Downey Jnr at the Iron Man premiere

Hollywood moguls spared no expense when they threw an extravagant party in honour of their hard-working star Gwyneth Paltrow last week.

They lavished about £60,000 on the private celebration at an exclusive London restaurant, inviting 30 of her closest friends and family and providing the finest champagne and cocktails, just as she'd requested.

But the studio chiefs were left disappointed when the actress failed to turn up – choosing at the last minute to go for dinner elsewhere.

Apparently, Miss Paltrow's decision to snub the party stems from a long-standing determination never to be photographed in public with her husband, Coldplay singer Chris Martin.

Although arrangements were in place to thwart the paparazzi at the chic Cocoon restaurant in Regent Street, Central London, the A-list couple decided not to run the risk.

Instead they went for an impromptu meal with Robert Downey Jnr, Paltrow's co-star in the new Iron Man blockbuster, and his producer wife, Susan Levin.

The decision left some of Paramount Pictures' most powerful executives making small-talk with fellow guests, including 31-year-old Mr Martin's parents, without Miss Paltrow.

The party took place immediately following Thursday's West End premiere of Iron Man and was intended as a "thank-you" to Miss Paltrow for her work on the gruelling promotional tour.

She had arrived at the screening in vertiginous stilettos and short skirt, virtually guaranteeing coverage for the premiere in all the major newspapers the next day.

She introduced the film at the Odeon cinema in Leicester Square but did not stay to watch it.

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Gwyneth Paltrow and husband Chris Martin try to hide their faces from the paparazzi

After the movie ended, party guests moved on to Cocoon. They included the film's director, Jon Favreau, and the Coldplay singer's parents – Anthony, a chartered accountant, and Alison, a music teacher – who had come from the family home in Devon with two of Chris's siblings.

But 35-year-old Miss Paltrow called a Paramount executive just minutes before she was due to arrive to tell them she wasn't coming to the party.

According to one studio insider, bosses were furious at the last-minute U-turn.

"Gwyneth was due to arrive at 10.30pm and had demanded a special entrance so that she and Chris would not be photographed together," said the source.

"They have a pact never to be photographed together and everyone had to go to ridiculous lengths to ensure no one could get a picture, including a ban on cameras inside the venue.

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Gwyneth gives her well-heeled feet a much-needed rest

"A lot of thought and money had gone into the party. Gwyneth had specifically asked for chilled bottles of Perrier Jouet champagne and some vodka cocktails to get the party going. Everything was in place and had been arranged around her.

"Apparently someone at Paramount got a call saying Gwyneth and Chris were going for dinner and wouldn't be coming. The senior execs were not at all happy.

"To make matters even worse, the other star of the movie, Robert Downey Jnr, was with her – so there were no stars at the party at all.

"There were a lot of embarrassed faces. No one could believe that all of Chris's family had made the trip to London, only for their son and daughter-in-law not to turn up."

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Gwyneth in a very painful pair of boots in London earlier this week

The 35-year-old actress has been teetering around Europe to promote her new movie The Iron Man

Another source close to the actress said Gwyneth was simply too tired to attend, after completing Press conferences in New York, Berlin and Rome before the London premiere.

"She had done all the promotional material she was contracted to do and clearly she'd had enough," said the friend.

"She spent an hour on the red carpet in Leicester Square chatting to fans and posing for pictures and decided to give the party a miss and go to Zuma restaurant instead.

"She and Chris were desperate not to be photographed together and thought they would outwit photographers. In the end, the paparazzi found out they were at Zuma anyway."

When photographers tried to snap the couple, Mr Martin tried to hide his face while Miss Paltrow shielded herself with her handbag.

Miss Paltrow's spokesman said last night: "Gwyneth was never meant to attend the after party.

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Friends say Gwyneth would really like to do another play in London after her success on the stage in 2005

Yummy mummy: Gwyneth sheds her earth mother image for a raunchy new look, showing lots of leg, a clean pair of Christian Louboutin heels, right, and a pair of black patent Burberry shoe boots, left

"She was at the taping of the Jonathan Ross show which ran late and then she went home to be with her children.

"Everyone was told weeks ago that she would not be attending.

"She has said many times that she deliberately does not make public appearances with her husband."

However, Miss Paltrow was photographed outside Zuma at 12.30 that night, hiding her face but with exactly the same ruby-coloured costume ring on her little finger as she had been wearing at the Iron Man premiere earlier in the evening.