This video can not be played Highlights: Superb England beat South Africa to set up World Cup final against Australia

The 'F' word came up again and again in the review into England's Ashes hammering. The players knew it. Staff knew it. And after England dropped seven catches on day two of the Test in Melbourne, the whole world knew it. England's fielding had not cost them the series but it was a clear problem. They also put down six chances when exiting the T20 World Cup against West Indies the previous autumn.

But Thursday's semi-final victory over South Africa at The Oval, with two fine Sophie Ecclestone catches and a perfect throw for a Danni Wyatt-Hodge run-out, was the clearest example yet of England's improvement. The secret? A sparkly disco jacket owned by the wife of the fielding coach…

Nick Wilton (left) played 17 first-class games and 19 List A matches in his career. The man tasked with improving England's fielding is long-standing coach Nick Wilton, the former Sussex wicketkeeper now dubbed DJ Wilton. His fielding 'disco nights' have become a feature of this World Cup. With the tunes blaring and while wearing his wife's jacket, Wilton has England's players charging around and taking high catches under the lights. Practice but fun practice. It has lifted England from those miserable days in Melbourne and Dubai.

"We do pieces of fielding to each song and he pumps the music up to try and get us all hyped up," vice-captain Charlie Dean said. "I love the way he gets us really passionate about fielding so it is fun every time."

This video can not be played Big breakthrough for England as Wolvaardt is caught early. There is, of course, more to England's improvement than a coach dressing like an ABBA tribute act. As well as Ecclestone's catches - a leap at mid-on and a nerve-jangler as the ball dropped over her shoulder at short fine leg - and Wyatt-Hodge's run-out, Charlie Dean also pulled off a direct hit dismissal in the win over New Zealand and Wyatt-Hodge took a superb catch in the tournament opener against Sri Lanka.

Fitness and fielding were two of coach Charlotte Edwards' priorities when she took over after the Ashes defeat. The former captain, who sprinted on to the field to congratulate her players during the timeout after Ecclestone's first catch, has calmly quietened talk of the issue. In one of her previous roles at Southern Vipers, Edwards used an electric scooter to follow and observe her players during their fitness sessions and one of her first moves after becoming England coach was introducing minimum fitness standards.

The new standards include a two-kilometre time trial, 30m two-way sprints (effectively shuttle runs), a test to assess explosiveness through a squat and a vertical leap, and another which gauges a player's maximum velocity. England posted clips from the gruelling sessions on their social media accounts at the start of the season. Videos of boat parties posted on players' own accounts are long gone under Edwards.

Wilton has been given free rein to improve England's fielding. Without any international fixtures this winter, he was able to work with the players on their training camps in Oman, Stellenbosch and Pretoria. There were more training sessions in the early-season gatherings at Millfield and Repton schools and at England's cricket centre in Loughborough.

"Progress happens with dedication over time and putting the work in," Dean said. "All our careers we put in the work but especially the last year."

This video can not be played 'That is brilliant!' - Sinalo Jafta run out by Danni Wyatt-Hodge. With the players buying in, there has also been a greater attention to detail. Dani Gibson, Freya Kemp and Linsey Smith – three fielders who often share the job of patrolling the boundary – practise their high catches or sprints to retrieve and return the ball. The powerful Gibson, one of England's quickest players across the ground, has repeatedly denied batters second runs with her quick work in this tournament – no more so than in the early stages against South Africa.

Bowler Lauren Bell regularly attempts flying one-handed catches in training – the type of opportunities that come in her position of short fine leg. It is obvious but appears to be working. "Being that extra bit more detailed in what we are trying to do has put us in great stead," Dean said.

And now there is one match remaining - Sunday's final against Australia. There would be no better opposition against whom to reinforce their improvement. "Lottie coming in after the Ashes when we were pretty poor, it is obviously something we wanted to work on as a team and we've had commitment from everyone to do that," captain Nat Sciver-Brunt said. "The plan from Lottie in how we do that has been executed by Nick, who encourages us to push ourselves as far as we can in the field and not put a ceiling on anything we do."

The work - and the jacket - has got England this far. Can they continue it under the most intense pressure? Women's T20 World Cup final: England v Australia. Ball-by-ball commentary on BBC Sounds and the BBC Sport website and app, which will also have live text commentary and video highlights. Sciver-Brunt leads superb England into World Cup final. The making of Dean - England's serene stand-in skipper.