Rarely has a player gone into a English domestic cup final bearing such a heavy responsibility as Michael Klinger, when he takes Gloucestershire to Lord's on Saturday. Success brings with it high expectations and Klinger's success in the Royal London One-Day Cup this season has been extraordinary: all-comers despatched with the broadest bat in the kingdom.

In the West Country, many talk optimistically of a Gloucestershire revival, recalling the time around the turn of the century when they dominated English one-day cricket, sensing that Surrey can be conquered to bring their first limited-overs trophy since 2004.

But it remains largely unproven whether Gloucestershire's revival runs deep or whether they have been sustained largely by the exploits of one Australian batsman flowering late. A Lord's final would not be the best time to have to answer it. Far better that Klinger, with 531 runs in the tournament to his credit - average 132.75, strike rate 92.50 - delivers one more time. Debate it later, preferably while holding a trophy, dripping with champagne.

It was a gorgeous late summer afternoon at Nevil Road, where Klinger has been clunking the ball into the new flats behind the arm at regular intervals for much of the summer. To an Australian used to long boundaries, they must seem to have been built on the outfield. Gloucestershire's players were in attendance for the pre-media day, grouped quietly as if they expected their marginal role. Most interviewers, this one included, predictably awaited a chat with an unassuming Australian whose reputation has never been higher.

Klinger has additional reasons to succeed, reasons that go beyond his captaincy of Gloucestershire, a county where his reputation has grown steadily in the past years, not just as a batsman but as a skilful, undemonstrative captain. No longer is he one of the least known overseas players on the circuit.

He has never represented Australia, but his target is a place in their World T20 squad in India in March. He is 35. Australia do not make a habit of giving 35-year-olds debuts in the modern age. Especially 35-year-olds they have occasionally dismissed without a second thought.

But he will not abandon hope while he is scoring so freely: the Sheffield Shield, the Big Bash League (where he was the leading run-maker last season), the Natwest t20 Blast and now the Royal London Cup. The runs keep coming and the statistics are beginning to overpower his date of birth.

And Adam Voges, Australia's third-oldest Test debutant since the war, made a hundred on Test debut in Dominica earlier this year, so even these days there are precedents for a late opportunity beyond the age of 35.

"There is no doubt that if I was scoring the runs at 25 that I have over the past four or five years then I would have played for Australia already," Klinger said. "That's my challenge now. In the past 18 months I have gone above and beyond that measure, so I have to keep doing that.

"I think the last 18 months where I scored over 1000 runs in Shield cricket in Australia and did well in the Big Bash and then followed it up here in England has been my best prolonged period. It's important to keep it going for one more game here and then the season back home in Australia. The next step is to hopefully play in the T20 World Cup."

It is tempting to propose that England has belatedly been the making of Klinger. After all, in his first seven seasons with Victoria, he made only two hundreds. He would have made his maiden hundred earlier, but Paul Reiffel, Victoria's captain, declared when he was on 99 and asserted that it was a team game. It was another four years before he ticked that one off.

This was rough justice, if justice at all, for a player who, at 15, had become the youngest to make a century in Victorian district cricket. He was preferred to Michael Clarke as captain of Australia Under-19, but Clarke has just retired from international cricket, a sated, feted Australian captain, whilst for Klinger the call has never come. The call that another Australia captain, Allan Border, said was virtually certain when he made a match-winning 80 on his one-day debut for Victoria, more years ago than he cares to remember.

He prefers to remember two breakthroughs. The first came when he moved from Victoria to South Australia at 27, was given the chance to bat at No. 3 and open in one-dayers, and made three first-class centuries, one a double, in his first six weeks. Adelaide, a sociable country town where a side could stick together, also suited him.

Easy runs on flat pitches, his detractors suggested, but one of them was at the Gabba, and it was more about him growing in maturity in response to the recognition that he was finally a senior player, assured of his place in the side, expected to deliver, not always giving way to those returning to the fold - be it David Hussey, Brad Hodge, Cameron White, Matthew Elliott.

The second breakthrough - his short-form breakthrough - came when he took South Australia to the Champions League semi-final in South Africa in 2010. It is surely an indictment of cricket beyond the international game - or those who promoted it, or perhaps those who sought to undermine it - that this world club tournament failed to gain appeal, but it did good by Klinger. His assessment gives succour to the view that the abandonment of the Champions League is bad for cricket.

"When I started to be successful in T20 cricket I captained Redbacks in the Champions League, we reached the semi, and ever since then I've been able to develop more of a short-form game and more of a 360-degree game," Klinger said. "We made the semi-final as underdogs, which for us was excellent. That made me really want to get better and better. You could see how T20 was going.

"I think my late development is just taking experiences in all conditions and learning from them. I have played in India a bit and I have played pressure games in domestic finals in Australia as well. Experiencing those pressure situations helped my cricket. Over the last six or seven years in Australia I have been able to be consistent in all three formats, which is something I'm proud of."

Even with his run-scoring at its height, there have been disappointments on the way. Last year, he moved to Western Australia after South Australia intimated his Shield place could no longer be guaranteed: two months previously he had scored a double-hundred.

He left hoping to gain a place in Australia's World Cup side. They won it without him. He was never thought to be in the running. The call, at 35, may never come - a likelihood that with the World T20 on the horizon he refuses to accept.

He came closest to an Australia call perhaps in 2009 when Marcus North was selected instead for a tour of South Africa because of his additional spin-bowling option and made a hundred on Test debut.

But back to Lord's - and the Royal London final against a Surrey side awash with the confidence of youth. What if Klinger fails? Richard Dawson, Gloucestershire's coach, fields such a provocative question with good grace. He asserts that they would be capable of taking it in their stride - and he has examples too, such as the time when they chased down Worcestershire's 264 for 8 in early August, Klinger an absentee, but the top four all making runs, to reach the quarter-finals.

"We are good enough," Dawson said. "That Worcestershire match was an interesting one. Michael gets the headlines as he should do, but people have also played around him and in the semi-final Hamish Marshall also took a lot of pressure off Michael by playing the innings he did.

Klinger also had the equanimity to consider the possibility of failure. "I failed once along the way in this cup run, so it can happen that you fail, but I will be doing everything I can as an experienced player to perform. The stats will show I have had a good series but I missed three games when I hurt my hamstring and we won two of those."

The most notable of those performances - if not necessarily against the best attack he faced - was his unbeaten 137 in Gloucestershire's semi-final win against Yorkshire at Headingley. It was a Yorkshire attack far removed from the one that has won the Championship for the second successive season, but Klinger's 137 not out from 145 balls possessed a certainty that stilled home expectations from an early hour. It was made all the more remarkable because his long-haul flight from Australia after a brief flight home to Perth did not land until Friday night, 36 hours before the game.

So what is the secret of getting over jetlag? "A lot of coffee on game day - it got me through," he said. "That and staring at the ceiling."

As he stared into the dead of night, he would have wondered about the possibility of a Lord's final, no doubt, as well as that elusive international cap. His brilliance made sure of the first, and, 20 years after he was first dubbed a star in waiting, he will not yet let go of the second. Surrey's young side will face an old pro still full of drive and ambition.