Rui Costa is the new world champion after outsprinting Joaquim Rodriguez at the end of a mammoth men's road race which Chris Froome failed to finish.
Costa and Rodriguez formed part of a four-man breakaway alongside Vincenzo Nibali and Alejandro Valverde on the last of 10 laps of a punishing 16.6km circuit around Florence and later forged clear on their own inside the last 2km.
Costa led out the sprint on a flat finishing straight and although Rodriguez fought back and almost drew alongside, the Portuguese rider fended him off to win by half a bike's length after almost seven and a half hours in the saddle.
Froome abandoned the race with just under 100km remaining having lost all of his team-mates and then been dropped by the front group.
None of the eight-man British team finished the race, with Sir Bradley Wiggins climbing off the bike early after falling off the pace and Mark Cavendish stopping as planned having led the peloton for the majority of the opening 100km.
Much of the 272.2km marathon was played out in torrential rain, which made for miserable riding conditions and caused a constant stream of crashes.
The race had been expected to be a battle between climbers, sprinters and one-day specialists and although all three groups were well represented going into the final lap, it was the climbers who prevailed.
The finishing circuit contained two key ascents - the 4.3km Fiesole and the steep, 600m Via Salviati - and it was on the Fiesole that sprinters such as Peter Sagan and Classics riders such as Fabian Cancellara and reigning champion Philippe Gilbert were distanced.
Italy's Nibali and Spain's Rodriguez did the damage by exchanging attacks up the climb and by the summit they had a small gap over Valverde, Costa and Colombia's Rigoberto Uran, who were the only three men able to follow.
Rodriguez on the offensive
Rodriguez attacked again on the descent and held a small lead going up Via Salviati, but the group - now down to four after Uran crashed out - came together at the top following a huge chase effort from Nibali.
Rodriguez attacked once again on the undulating run to the finish and opened up a small gap, but Costa set off in pursuit inside the last 1,500m, caught him with 200m to go and still had enough energy left over to win the subsequent sprint.
He said afterwards: "I was waiting for the sprint all day, saving as much energy as possible to get to the finish. I was hoping my legs wouldn't fail me - they didn't. It was the most beautiful win of my life."
Costa's victory completed an outstanding season in which he also won the Tour de Suisse and two stages of the Tour de France.
Earlier in the day, Poland's Bartosz Huzarski formed part of a five-man breakaway and rode for more than 220km at the front of the race, finally being caught just under 30km from home.
Men's road race result
1 Rui Costa (Por), 7:25:44
2 Joaquim Rodriguez (Spa), same time
3 Alejandro Valverde (Ita), +15
4 Vincenzo Nibali (Ita), st
5 Andriy Grivko (Ukr), +31
6 Peter Sagan (Svk), +34
7 Simon Clarke (Aus), st
8 Maxim Iglinskiy (Kaz), st
9 Philippe Gilbert (Bel), st
10 Fabian Cancellara (Swi), st
DNF Chris Froome (GB)
DNF Bradley Wiggins (GB)