He urged people to check in on their friends who they haven’t spoken to for a long while as it could “be the last time.”
It read: “Hi Sean, I hope you and your family are doing okay. Did Countdown last week and missed having you there.
Born in Woking, Surrey, Lock left school in the early 1980s and began working on building sites but developed skin cancer, which he blamed on over-exposure to the sun. He made a full recovery and focused on a career in comedy.
One of his first professional TV appearances was in 1993, alongside Rob Newman and David Baddiel on their signature TV show Newman And Baddiel In Pieces.
He script-edited 1998 BBC Two series Is It Bill Bailey? and had his own show on BBC Radio 4 called 15 Minutes Of Misery, which was later expanded into 15 Storeys High.
The show was set in a tower block and centred on a pessimistic character called Vince (played by Lock) and his flatmate Errol (Benedict Wong).
In 2005 Lock became a regular team captain on the panel show 8 Out Of 10 Cats, a role he held for 18 series.
Between 2006 and 2007 he hosted Channel 4 series TV Heaven, Telly Hell, in which he invited celebrities to share their own selection of TV’s triumphs and tragedies.
Guests included Alan Davies, Johnny Vaughan, David Mitchell, Bill Bailey, Johnny Vegas and Nick Hancock.
Lock also appeared on panel shows including Have I Got News for You, QI and They Think It’s All Over.
‘What a loss’
QI host Stephen Fry said: “I think it safe to say that the best episodes of QI that I was involved with were always the ones where Sean Lock was a guest.”
A tweet from Fry added: “Such complete brilliance in every comic direction. What a loss. My heart goes out to his family.”
In 2000 Lock, who was also a husband and father-of-three, won the gong for best live stand-up at the British Comedy Awards.
Strictly winner and comedy star Bailey told BBC Radio 5 Live: “It’s a devastating loss, personally and to comedy.
“He was my dearest friend and we’ve known each other more than 30 years and we’ve known he was ill for some time, but even so it’s still a shock when the day comes.”