David Walliams is set to take the rest of the year off to recover from emergency back surgery.
The star, 42, will have an operation this week to fix a disc he tore during his gruelling charity swim in 2011.
The Little Britain star and Britain's Got Talent judge apologised for postponing next month's World of Walliams book event at London's Palace Theatre.
David told fans: "Unfortunately the operation on my back is long overdue and can't wait a moment longer. After Tuesday the doctors have ordered me to rest for the remainder of the year so I can recover."
A message on the World Of Walliams website said: "David Walliams is due to undergo emergency back surgery this week and has been advised by doctors to cancel all work commitments for the remainder of 2013... David has suffered from a long standing back injury since he swam the Thames in aid of Sports Relief."
The Daily Mirror said that David has been on medication since his 14-mile charity swim.
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