Confidence in the men behind him was crucial in Jason Roy's fearless approach to an innings that grew into the biggest-ever ODI century by an England batsman, guiding the tourists to the highest successful chase in a match at the MCG.

Roy teed off early on against Mitchell Starc and Pat Cummins, showing a willingness to "chance his arm" in the words of the Australia captain Steven Smith that epitomises the daring of England's limited overs set-up since they started from scratch in the aftermath of a dire 2015 World Cup campaign.

From a half-century that took only 32 balls, Roy settled in alongside Joe Root to surpass Alex Hales' previous England best of 171, and said he was able to do so because of how firmly England's batsmen believed in each other. Also important was the resolve of England's limited-overs players to bring positive vigour to the touring team after the trials of an Ashes series lost 4-0.

"I think the main thing is knowing how good each other is," Roy said. "Knowing our middle order is incredibly special and talented and can win games from anywhere. To have that behind you gives you so much confidence at the top of the order. Knowing each other's roles is important and everybody knows their own roles. That's something we've built on and got a good foundation now. But it's one win, four more games to go.

"It was an absolute honour to be out there on the MCG and to get a score like that, to win our first game of the series is incredibly special. There's not many words right now but I'm sure in the next couple of days I'll have a bit more. It is extremely special, especially after the Test series.

"It was obviously quite tough, we knew the boys were going to be a bit down and it was our task to come in and lighten up the mood, bring the positivity and get the boys going. I think we've done it and there's a lot more smiles going on now. It's a good start to the series but it's by no means finished, we want to be as ruthless as possible."

Roy's call-up to England more or less coincided with the change in approach that accompanied the emphasis of Andrew Strauss, Trevor Bayliss and Paul Farbrace on a more proactive brand of limited-overs cricket, aided by the leadership of Eoin Morgan. He was dropped from the side during the Champions Trophy, after his form tailed off during the first half of 2017, but the enforced absences of Ben Stokes and Alex Hales created an opening that he has charged back through in recent months.

"It's been a while coming, I had a very tough year in 2017 ... being dropped from the side and then being brought back into it towards the end of the year," Roy said of his personal turnaround. "It kind of gave me a bit of a kick to recognise where I'm at, where my preparation is and start building up a platform to get ready for internationals. It has turned round incredibly quickly, that's the nature of this game - especially in one-day and T20 cricket.

"I haven't been doing too many things too differently, I had a long net session yesterday with a couple of the coaches and was playing the ball a lot later but other than that all my routines have been pretty similar since I've started. I think cricket tests you and you start questioning yourself and start questioning your preparation and how you're playing the ball and all this sort of rubbish, and it was just a case of clearing my head.

"I've got 50 overs to bat and if I bat 50 overs on good pitches in Australia I'm going to get to a good score, and that was my mentality. I didn't go out there thinking I'm going to go all guns blazing, I went out there and started as I've started every other net session since I've been in Australia, trying to play the ball late, playing strong shots and all these cliches, but it was just a case of finding the gaps. Some innings you hit them straight to fielders, some innings you don't."

Roy now owns two of England's four highest ODI innings, including 162 against Sri Lanka at The Oval in 2016, while Hales' innings took place against Pakistan at Trent Bridge in the same summer. Robin Smith's unbeaten 167 against the Australians at Edgbaston in 1993 had long stood as the high water mark, but Roy said 200 was no longer out of the question. "Yeah I hope so," he said. "I think we've got ourselves closer and closer, we're edging ourselves towards the 200. It's by no stretch of the imagination impossible for us."

Never in his ODI career had Roy batted for more than 40 overs, and he said he had been able to mentally reset in the aftermath of the moment on 91 when he was given lbw to an Adam Zampa googly. Roy successfully referred it after conferring with Root, and had his ears stung by a liberal offering of unsolicited advice from the Australian fielders.

"I kind of turned away because I did feel I might've been outside the line," Roy said. "Then I heard them cheering and saying a few things and I was like 'you're kidding me' and then looked at Rooty and was like 'come on mate, surely it's outside the line' and he's like 'yeah outside the line 100%'. Then they started going on about me if I'm actually playing a shot and all this sort of stuff and there was a bit of that, but I think that kind of switched me into another innings, got me motivated to go big and go long."

Though they ended up needing to chase more runs than had ever been successfully run down in a match at the MCG, England were given a collective spring in their step by the early venom shown by Mark Wood, fit again after his latest injury problems. David Warner's early exit to a vicious rising ball, and several other deliveries that tested the reflexes of Steven Smith and Aaron Finch, showed that the England ODI team were going to go after the hosts.

"Yeah too right, a bit of their own medicine was quite nice," Roy said when asked about whether it had been helpful to see Austrlaia's batsmen discomforted by speed. "Obviously the boys have copped it a bit over the last month or so and to see Woody coming in and doing that is a huge positive for us and he's a massive asset I think."