The 1979 Christmas Ball was broadcast on 24th December 1979, and was the show's first Christmas Special, and the last show of the 1970's. This was the 67th I'm Sorry I Haven't A Clue show to be broadcast, with Graeme Garden being the only person to appear in all 67.
It featured Humphrey Lyttelton in the chair with Graeme Garden, John Junkin, Tim Brooke-Taylor and Willie Rushton, with Colin Sell at the piano.
A Pro/Celebrity Special version of Mornington Crescent was played. The Special Guest joined Humph, but was not introduced. Humph explained The Parallel Transfer Rule – Any team that gets 2 positions ahead of their opponents can transfer to a corresponding position on a parallel route without losing a turn.

The first round was played so the special guest could get used to the rules. During the second round Willie got to Mornington Crescent before the guest got to join in. Humph then apologised to 'Sir Alec'.