From
Wikipedia
"On 18 April 2008 Jon Naismith, the producer of I'm Sorry I Haven't A Clue, announced the cancellation of the upcoming spring series of ISIHAC owing to Humphrey Lyttelton's hospitalisation to repair an aortic aneurysm. Rob Brydon was asked to deputise for Lyttelton during the tour shows.
Lyttelton died following his surgery on 25 April 2008"
...Dollis Hill