Veteran singer Tony Bennett has cancelled his sell-out show with Lady Gaga after coming down with the flu.
His publicists dismissed rumours the 88-year-old has had a heart attack, insisting that he is just ill and has nearly lost his voice.
The crooner is said to have reluctantly cancelled the concert on doctor's orders.
The two stars were due at London's Royal Albert Hall where they have been performing numbers from their Cheek to Cheek jazz album.
The cancellation comes just a day after Prince Harry watched the pair perform there in a charity concert to raise money for WellChild, which he is patron of.
Last night Bennett had looked well and was chatting happily to the prince ahead of taking to the stage with Lady Gaga.
He apologised on Twitter, telling his 121,000 fans: " Sorry to not be singing in London tonight. I love my fans in the UK and appreciate all the well wishes to get over this flu quickly."
Gaga told her 47.4 million followers on Twitter: "H ey everybody! Don't worry about Tony, he's OK! That's just showbiz sometimes. We'll catch you next time, we got you!" with a heart symbol.
A statement from Hyperactive Publicity, which represents Bennett, said promoters Live Nation confirmed the concert has been cancelled.
It said: "Unfortunately, Tony Bennett has come down with a flu virus which has prevented him from performing the second of two sold-out shows in London.
"Ticket holders are instructed to retain their tickets to this event pending more information.
"Fans who have purchased tickets online will be notified via the ticket outlets as soon as additional information is available."
A spokeswoman for the firm insisted the singer has not had a heart attack, and said discussions were taking place to see if the concert could be rescheduled.
Explaining how he and Lady Gaga collaborated on their album, Tony Bennett told Prince Harry: "I heard her personally and said we have to get together."
Harry replied: "I can't believe you have the energy, I don't know how you do it."
But Lady Gaga laughed and replied: "He runs circles round me. Wait until we get on stage."