Great Britain continue to impress in the rowing at Eton Dorney

The Great Britain lightweight men's four underlined their Olympic gold medal potential with a commanding semi-final victory at Eton Dorney.

Richard and Peter Chambers, Chris Bartley and Rob Williams unleashed a powerful sprint for the line to surge clear of Switzerland in the final 500 metres.

The British crew won in five minutes 59.68 seconds, just quicker than the time posted by chief gold medal rivals Denmark in winning the second semi-final.

The lightweight four have existed under the radar for much of the Olympic build-up, with the likes of Katherine Grainger, Greg Searle and the heavyweight men's four dominating the headlines.

But they won bronze at last year's World Championships and rounded off a successful World Cup campaign with gold in Munich last month.

That triumph was described by GB Rowing performance director David Tanner as "sensational" - but there could be better to come from Britain's lightweight four in Thursday's final.

Britain's tally of Olympic finalists has now risen to seven, with the women's eight and the men's double scull of Bill Lucas and Sam Townsend both progressing today.

The underperforming women's eight, bronze medallists at the World Championships last year, claimed the last available place in Thursday's final by finishing fourth in today's repechage.

Britain were six seconds behind race-winners Holland and they will have to improve markedly if they want to contest the medal positions - but Olivia Whitlam insisted no-one should write them off.

"I made the final at the last Olympics four years ago, it is not what we are here for. We need to go out and show what we are actually capable of," Whitlam said.

"We beat the Dutch in Munich last month so [today's result shows] how far off we are. At the moment we are all a bit hacked off. It is frustrating to underperform.

"I would never discount this group of eight girls with our backs against the wall. We like a fight. We are not necessarily the top-ranked girls so every day is a fight to prove ourselves so we know how to do that.

"This is when something like that comes in useful. We know how to come back. We have just got to."

Townsend, who is engaged to Natasha Page from the women's eight, and Lucas finished third in their semi-final behind the Slovenian crew, who were Olympic champions 12 years ago, and Lithuania.

There was a shock in the first heat with reigning Olympic champions Australia and world silver medallists Germany failing to qualify.

Alan Campbell moved smoothly into the semi-finals of the single sculls with a length victory over Germany's Marcel Hacker to underline his own podium credentials.

Campbell, a bronze medallist at the 2011 World Championships, controlled the race after establishing an early lead over the veteran German.

Competition is fierce in the single scull, with Hacker a recent gold medallist at the Munich World Cup and so to qualify with a race victory was a confidence boost for Campbell.

"I'm really happy with that, really pleased," he said.

"In my last World Cup result in Munich I finished behind Lassi [Karonen] and Marcel and I thought I was better than that.

"I feel today I've justified that and put it to rest and am ready for the semi. It was a confidence booster.

"I feel in very good form, but I've got to keep a lid on it, I don't want to get too over excited or anything else and when it comes to the final the gloves are off and we'll go out fighting."

New Zealand's Mahe Drysdale remains the favourite to add Olympic gold to his five world titles and he won the first heat, ahead of Belgium's Tim Maeyens.

Karonen of Sweden is hitting form at the right time and he won the third quarter-final, while Ondrej Synek won his heat with reigning Olympic champion Olaf Tufte scraping through in third place.

PA