Benjamin Thomas enjoyed the biggest win of his road career after securing a surprise victory in Stage 5 of the Giro d'Italia on Wednesday. A four-time world champion on the track, Cofidis rider Thomas had never before won a Grand Tour stage but edged out Michael Valgren and Andrea Pietrobon following a breakaway attack. The four-man break escaped the peloton after the final intermediate sprint of the day, with 80 kilometres left to ride, and held off the chasing pack despite the best efforts of the main sprint contenders' teams. Italian Pietrobon (Polti-Kometa) looked set to reach the line first after the 178km ride from Genoa to Lucca, but his push for victory inside the last kilometre came too early, and he was caught before the finish. Pietrobon had to settle for third place, with Denmark's Valgren (EF Education-EasyPost) coming in second behind Thomas, giving the Cofidis team their first victory this year. Enzo Paleni completed the top four and next across the line was points classification leader Jonathan Milan at the head of the chasing pack as an expected challenge from the sprinters failed to materialise. Tadej Pogacar, the two-time Tour de France champion, finished safely in the peloton to remain 46 seconds ahead of Geraint Thomas and 47 seconds ahead of Daniel Martinez in the overall lead. “It was like a long, long, long team pursuit,” said Frenchman Thomas when asked how his track background helped in the break. “We did an amazing break and I don't believe it. It was really hard in the finale, every pull was full gas. It's unbelievable. “I bet nobody bet on the attackers today and the final was really critical because with the attack with 1km to go by the Italian rider, I said, 'OK, I risk to lose' but I don't close the gap and everything is perfect to do. I don't know what to say, honestly. “I knew all the road of the final because I train there sometimes. It was helping me to know with the cobbles and the corners and it's a nice thing to live in Italy, it means a lot for me.” The main group arrived on the line 11 seconds behind the winner, with Pogacar safely in the top 30, maintaining his lead over Ineos Grenadiers rider Geraint Thomas. Thursday's Stage 6 will take the riders along a tough 180km route from Viareggio to Rapolano Terme that will take in gravel sectors in Strade Bianche territory close to Siena. “Today was quite an interesting day, the last one hour or so was really, really fast, it was incredible and the speed in the last 50km was just so high," said race favourite Pogacar. “Coming to Lucca was really intense and crazy, the breakaway stayed in front and the sprinters were chasing them but unfortunately for them they didn't catch them. “The breakaway stayed ahead because it got away late and nobody managed to reel them in. Tomorrow is a stage where we need to be careful not to lose any time and to stay safe.” 1) Benjamin Thomas (Cofidis) 3 hrs 59 mins 59 secs 2) Michael Valgren (EF Education-EasyPost) same time 3) Andrea Pietrobon (Team Polti-Kometa) 4) Enzo Paleni (Groupama-FDJ) +3 5) Jonathan Milan (Lidl-Trek) +11 1) Tadej Pogacar (UAE Team Emirates) 19 hrs 19 mins 15 secs 2) Geraint Thomas (Ineos Grenadiers) +46 3) Daniel Martinez (Bora-Hansgrohe) +47 4) Cian Uijtdebroeks (Team Visma-Lease a Bike) +55 5) Einer Rubio (Movistar) +56