Cheryl Cole leaves London's Dorchester hotel after performing at a millionaire's 70th birthday party

The group were invited to perform a 45-minute set at the 70th birthday party of British billionaire Eddie Healey.

He hired Cheryl Cole, Sarah Harding, Kimberly Walsh, Nicola Roberts and Nadine Coyle as a surprise for his grandchildren on Saturday night.

The wealthy bachelor reportedly took a shining to Cheryl during the band's performance and although the singer told the birthday boy she was married, she failed to wear her wedding ring.

Mr Healey, who with his brother Malcolm has amassed a £1.9 billion fortune from property and the kitchen business, splashed out a whopping £475,000 for his own private bash including £350,000 on hiring the ballroom for his 300 guests.

He covered the food and drinks bill for everyone — and even requested that the ballroom be re-carpeted.

Other celebrities booked for the bash, held at the swanky Dorchester hotel in Lonson, were comedians Russ Abbot and Bobby Davro.

The attention will surely come as a confidence-boost to the singer, 24, who has been pictured recently looking painfully thin following her separation from footballer husband Ashley.

One friend told the News of the World: "Cheryl's weight has plummeted. She was a size ten. Now she has to buy size six outfits.

"Cheryl's closest friends are urging her to eat. She looks painfully thin and her appetite seems to have disappeared.

"She's trying to move on and make a go of things with him."

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Monochrome: Kimberly Walsh opts for a black outfit while a more demure Nicola Roberts (right) chooses an angelic look in white

Big spender: the party was paid for by billionaire Eddie Healey

She said: 'I've had to watch my weight and do rigorous workouts to keep trim.'

The girls also recently played at an 18th birthday party for the daughter of a millionaire.

They entertained around 150 guests alongside fellow stars Westlife in a huge marquee at Kenwick Park Hotel in Louth, Lincolnshire.

Both groups played greatest hits sets with the Irish boyband leading a Happy Birthday chorus to the teenager.

She is said to be the same schoolgirl who Pop Idol winner Will Young sang for on her 16th birthday.

Meanwhile, the four girls have been working hard at their South-East London rehearsal venue ahead of a 22-date tour, which kicks off in May.

Intended to showcase their current album Tangled Up, it is sure to be a glitzy affair.

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Bombshells: Sarah Harding and Nadine Coyle sport matching blonde hair