Tour de France champion Chris Froome abandoned the Road World Championships men's elite race amid treacherous conditions in Tuscany that led to a disastrous day for Great Britain.
Geraint Thomas was the last of the eight Britons to pull out with 30 kilometres of the 272.5km course remaining and the Welshman described what he witnessed on the roads as "carnage" after torrential rain resulted in a succession of crashes.
Sir Bradley Wiggins and Mark Cavendish fell early on, the victims of a pile-up involving multiple riders, and Steve Cummings was hit by a puncture.
With around 80km of the course left and having lost most of his team-mates, Froome withdrew from a race won by Portugal's Rui Costa, who pipped Joaquim Rodriguez of Spain in a sprint for the line.
It ended Froome's bid to become the first man since Greg LeMond in 1989 to win the Tour de France and World Championships road race in the same year.
"Even before going out on to the circuit there were crashes everywhere. It's just the weather - it hadn't let up all day," the 28-year-old Froome told the BBC.
"It had been raining solidly and all the drains started flooding and in some points on the road it was quite deep with water.
"People were trying to move up on the sides but were getting stuck in the gutters, causing most of the crashes.
"The conditions were the same for everyone so there are no excuses, we just weren't there.
"After three laps the splits started happening and I saw that I didn't really have any team-mates with me and thought 'this is not going to happen for me'.
"This would have been a good exercise for Rio in 2016 but after coming up empty-handed, we'll have to go back to the drawing board.
"Having trained so hard coming into this and making it such an important goal, a result here would have been a fantastic way to finish the season, but in these conditions it just wasn't to be."
Thomas admitted that once the hilly course from Lucca to Florence had claimed Wiggins and Cummings, it was all over for Froome and Great Britain.
"It wasn't the best day on the bike. We had Chris as the leader and he wasn't on a great day," Thomas told the BBC.
"We had a little bit of bad luck with Steve puncturing and that wasn't the weather for Brad.
"Brad and Steve are our two strongest to be with Froome and we lost them as soon as we hit the circuit.
"It's not ideal and the rest of us didn't have the legs to do anything in the final. We all committed to getting Chris there, it just wasn't to be.
"It was carnage out there - as soon as you drifted into the second half of that peloton there were crashes everywhere. I saw at least five or six crashes in front of me."
The appalling weather made it a nightmarish experience for the riders in a day of high drama.
Costa and Rodriguez pulled away in the final kilometre but it was the Portuguese, who led for the first time, who had the strength to claim the rainbow jersey with Spain's Alejandro Valverde finishing third.