Julian Arredondo climbed to a fine solo victory on stage 18 of the Giro d’Italia as fellow Colombian Nairo Quintana comfortably retained the leader’s pink jersey.
Arredondo formed part of the day’s 14-man breakaway but later rode clear on his own to claim the first Grand Tour win of his career and all but seal victory in the mountains classification, which he has led since stage eight.
Fabio Duarte, another Colombian, crossed the line at Rifugio Panarotta 17 seconds later in second place, while Irish Team Sky rider Philip Deignan produced a spirited performance to take third, 37 seconds down.
Quintana finished just ahead of Rigoberto Uran, who is second overall, to consolidate his 1min 41sec lead in the general classification, but Cadel Evans dropped from third to ninth after losing more than a minute and a half to his rivals on a disastrous day.
Two seconds separate trio
Evans’s struggles were brought about by Pierre Rolland, who had been fourth overall but now climbs into the final podium position, 3min 29sec back, after a pair of attacks in the final 4km thinned the main group of favourites down and caused the veteran Australian to be dropped.
The day’s other mover was Fabio Aru, who attacked in the final 400m to steal a handful of seconds on his rivals and rise to fourth overall. Incredibly, he is now on the same time as fifth-placed Rafal Majka, with both riders just two seconds adrift of Rolland.
The 171km stage ended in the Giro's eighth of nine summit finishes and with the potential for a breakaway winner, a large escape group packed with climbing talent moved clear early in the day.
Thomas de Gendt, a former Giro stage winner, attacked at the bottom of the 16.8km, category-one ascent to Rifugio Panarotta, but a spate of counters saw the Belgian caught with just over 6.2km remaining.
Arredondo, who had earlier taken maximum mountains points at the day's first two climbs, attacked immediately and although he was soon reeled back in, his move whittled the breakaway group down and left only himself, Duarte, Deignan and Franco Pellizotti left in contention for the stage win.
After Pellizotti had tried and failed with a surge of his own 5km out, Arredondo attacked for the second time 1km later and this time no one could follow. Duarte and, impressively, Deignan both tried to give chase, but neither could make inroads.
Arredondo said: "I didn’t imagine for a moment that today could be my day. My coach, Josu Larrazabal, believed in me. At the foot of the final climb, I wanted to attack, but Josu said, 'Take it easy, not yet'.
"Then, much higher up, he said, 'Julián, now!' So I won the stage because of his advice. He gave me the calm and the patience, and the day ended perfectly for me. I dedicate this stage win to him."
Stage 18 result
1 Julian Arredondo (Col) Trek Factory Racing, 4:49:51
2 Fabio Duarte (Col) Colombia, +17secs
3 Philip Deignan (Ire) Team Sky, +37
4 Franco Pellizotti (Ita) Androni Giocattoli-Venezuela, +1:20
5 Edoardo Zardini (Ita) Bardiani-CSF, +1:24
6 Thomas de Gendt (Bel) Omega Pharma – Quick-Step, +1:38
7 Ivan Basso (Ita) Cannondale, +1:43
8 Dario Cataldo (Ita) Team Sky, +1:59
9 Fabio Aru (Ita) Astana, +2:43
10 Nairo Quintana (Col) Movistar, +2:46
1 Nairo Quintana (Col) Movistar, 77:58:08
2 Rigoberto Uran (Col) Omega Pharma – Quick-Step, +1:41
3 4 Pierre Rolland (Fra) Europcar, +3:29
4 Fabio Aru (Ita) Astana, +3:31
5 Rafal Majka (Pol) Tinkoff-Saxo, +3:31
6 Domenico Pozzovivo (Ita) Ag2r-La Mondiale, +3:52
7 Ryder Hesjedal (Can) Garmin-Sharp, +4:32
8 Wilco Kelderman (Ned) Belkin, +4:37
9 Cadel Evans (Aus) BMC, +4:59
10 Robert Kiserlovski (Ned) Trek Factory Racing, +8:33