Sir Elton John has cancelled a concert in London's Hyde Park because of appendicitis.
The star was due to headline the gig on Friday night, but called in doctors during his European tour.
He was topping a bill which also features Elvis Costello and Ray Davies.
Sir Elton, 66, is now on an intensive course of antibiotics.
A statement on behalf of the singer said he had been diagnosed with an “appendix abscess surrounding retrocaecal appendicitis”.
He is expected to undergo surgery in the UK in the next few weeks, when doctors are sure they have reduced toxins around the inflamed appendix sufficiently.
Doctors advised him to cancel all forthcoming shows from his current tour, including the Hyde Park show, which is part of the Barclaycard Presents British Summer Time Festival.
He will not be back on stage until fully recovered from the surgery and the damage caused by the abscess.
A spokesman said: “Elton is incredibly disappointed to postpone these tour dates. To know that he made such super-human efforts and continued to perform to thousands through his illness only confirms his dedication to his European fans.
“He is eager to be back on top form and return to play the remaining shows starting in early September 2013.”
Sir Elton was confirmed only today as one of the stars due to play the iTunes Festival at London's Roundhouse in September, alongside Arctic Monkeys and Justin Timberlake.