The victory puts Johnston and the CCS Canberra team on top of the National Road Series leaderboard with eight legs remaining.

The dual discipline cyclist placed third last year and wasn't going to settle for another podium finish in Australia's oldest one-day classic, beating Michael Freiberg, Mark O'Brien and Benjamin Perry in a bunch sprint.

Johnston says he's still coming to terms with the victory, labeling the finish as one the best moments of his career.

"I've won Australian championship on the mountain bike, but in terms of victories that have meant a lot to me this is right up there," Johnston said.

"I was quite emotional after the race. It's such an epic race - it's so long and has so much history.

"It's such a lottery as well, to get into the winning move then win it. I was speechless.

"Just to win it after so many challenges throughout the day, that finishing moment is certainly one of the best moments of my career."

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The toughest part of the 267 kilometre race for Johnston was the first phase, to make the right move to put himself out the mess.

It took nearly 140 kilometres for a break to be established, three groups attacked and surged ahead before merging to form a leading group of 37 riders.

Johnston was part of a five-man break who rode away from the initial breakaway group at Timboon. He went on to win the final intermediate sprint, the Victorian 200km Championship', before claiming the overall victory.

"The distance and sprint at the end is the challenge but for me, it's more the first phase because there's so many moves," Johnston said.

"I had really good team support in the first part of the race which was really helpful.

"Getting into the first move was the biggest challenge for me and at that point, I'm really confident within myself to just ride steady with the guys. The finish is anyone's win.

"I was unusually patient for whatever reason, I had confidence I could wait for the sprint.

"Certainly that patience is something I haven't always had and I guess as you get older you get more patient. It really paid off."

The 28-year-old cyclist will switch disciplines and return to the mountain bike when the Otway Odyssey kicks off in Melbourne this weekend.

His cycling team is now eyeing the second leg of the NRS, the Tour de Brisbane on April 5.

"I've got a solid career going with mountain biking, then sometimes I jump across a few events with the CCS team," Johnston said.

"We were planning on doing a few events throughout the year, I think we'll now head to Brisbane for the next round.

"I don't know whether the team is keen to chase a bit more now that we're in the lead. We're going up against much bigger and stronger teams.

"It's very cool to give the team the lead in the NRS, they're very passionate about it."

Canberra's Michael Rice also claimed a victory in Warrnambool, winning the inaugural Middle Island Criterium on Sunday.