Tony Bennett was forced to cancel his concert at London's Royal Albert Hall last night (09.06.15) after catching a flu virus.

Tony Bennett with Lady Gaga and Prince Harry at the first of their Royal Albert Hall concerts

Tony Bennett with Lady Gaga and Prince Harry at the first of their Royal Albert Hall concerts

The legendary jazz singer was set to perform alongside Lady Gaga - with whom he collaborated on the album 'Cheek to Cheek' - at the sold-out gig but had to pull out after falling ill.

Dismissing rumours he'd suffered a heart attack, Tony wrote on Twitter: "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."

Lady Gaga, 29 - who, along with Bennett, met Prince Harry before performing at the first of their two scheduled charity concerts earlier this week - also took to social media to apologise for the cancellation.

She said: "Hey everybody! Don't worry about Tony, he's ok! That's just showbiz sometimes. We'll catch u next time, we got you! (sic)"

The reason for the cancellation was also confirmed by Bennett's spokeswoman.

She said: "Live Nation has confirmed that the performance by Tony Bennett and Lady Gaga previously scheduled for this evening at the Royal Albert Hall is not taking place.

"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."

Meanwhile, Lady Gaga and Bennett will reportedly serenade Hillary Clinton - whom the 'Poker Face' hitmaker is a long-standing supporter of - at a fundraiser for the presidential candidate at New York's Plaza Hotel later this month.

Tickets for the event - which is set to take place on June 27 - are being sold for $2,700 each with a limited number of $1,000 tickets.

A source told the New York Post newspaper's PageSix: "They're not sure if it'll be a seated affair or if people will be standing - it's a pricey night to be standing."