Hamilton was part of the group of the favourites that had hunted down the breakaway, alongside teammates Jack Haig and Simon Yates.
Team leader Simon Yates made the biggest of the attacks on the final climb of the Ospedaletto, 7 kilometres at 6.2 per cent, drawing major contenders with him including Geraint Thomas (INEOS Grenadiers) and Stage 3 winner Michael Woods (EF Education First). The other climbers managed to catch the attackers on the descent into Cascia, with Hamilton attacking straight past as he joined from behind.
He escaped with Masnada, they worked well together to keep away from the chasers, and the Ararat local managed to overcome the normally rapid sprint of the Italian to claim his maiden WorldTour win.
“I just hung on over that final climb and I was in that second group when Yates attacked ahead," said Hamilton. "When we got back on, I saw my own opportunity and with the speed and momentum we had I was able to get away."
"I was very lucky to have Masnada there with me because I don’t think I could have done that myself and we worked well together. On paper, Masnada is probably faster than me so I was a bit worried about that and tried to make him do the last 500 metres or so and that worked in my favour in the end."
Hamilton moved up on the general classification to fourth overall, 27 seconds in arrears of race leader Michael Woods. Mitchelton-Scott is using the race as a dress rehearsal for the Giro d'Italia, where Hamilton and Haig will ride as key support for 2018 Vuelta a Espana winner Simon Yates. Yates currently sits behind the 24-year-old Australian on the general classification, but Hamilton was under no illusions as to who the team was working for.
“Simon is still our overall leader, so this win is a bit of a bonus but for me it is nice to step up," said Hamilton. "I take my opportunities when I can and I am lucky to have a leader like Simon that also lets his teammates have opportunities."
Hamilton has long been regarded as one of Australia's best general classification prospects for the Grand Tours, and results like this show that he's living up to his billing.