London Mayor Boris Johnson has been wheeled out throughout the year in promotion of the RideLondon cycling festival.
The regular rider will take part in the 100-mile challenge on Sunday.
"My team has told me I will never make it," Mr Johnson said. "They think I am too clapped out to cycle 100 miles but the more they discourage me, the more determined I am to have a crack."
More top news
A hitchhiking robot that won the hearts of fans worldwide has met an untimely end after being vandalised on its trip across the US.
Rules could be changed to remove support for failed asylum seekers living in Britain with their families, a Home Office minister has said.
More than 50 dog surfers of all breeds and sizes joined an annual dog surfing competition in California