Later quarter-final successes on the WBT's portable rink at Potters Leisure Resort in Hopton-on-Sea saw Englishmen Greg Harlow and Mark Royal also book places in the last four – which sees the top four seeds through to the world semi-finals for the first time in living memory.

Alex Marshall, the record five-time world champion from East Lothian, faced Commonwealth Games gold medallist Robert Weale – and, after dropping the first set, secured the second by an eight-shot margin before taking the first end of the tie-break.

Welshman Weale won a toucher with his first delivery and, holding shot, delivered his final bowl to cover the back position.  But, with three inches to draw the shot, fourth seed Marshall replied with an inch-perfect delivery to win the match 7-8, 9-1, 2-0.

"That was a top-class bowl from a world-class player," exclaimed BBC TV commentator John Price.

Later, three-time champion Paul Foster survived an almost identical situation against widely-respected England captain Andy Thomson.  Second seed Foster took the opening set but dropped back as his tenth-seeded opponent built up a nine-shot lead in the second to draw level.

With all to play for in the tie-break decider after each had won an end, Thomson drew the shot with his opening delivery.  But, after failing to kill the end with his second bowl and with Thomson still holding shot, Foster delivered his final bowl with perfect weight to nudge the shot bowl away from the jack to clinch the end – and a dramatic 7-6, 2-11, 2-1 victory.

"I was beaten by the WBT's Shot of the Year last year – and it looks as if the same has happened to me again this year," said a stunned Thomson afterwards.  "I thought we both played well – it was a great game, but I'm obviously disappointed.

"But, full credit to Paul," added the 55-year-old from London who won the world title in 1994 and 1995.

Foster admitted that his match-winning delivery was "one of the biggest bowls of my career – and playing it here in the world championship makes it even better.

"It's the hardest shot on the carpet.  You'd probably play it a hundred times and get it once," Foster explained.  "I saved my best till last!"

When interviewed post-match by BBC TV presenter Rishi Persad, the 37-year-old from Troon in Ayrshire paid tribute to Thomson:  "The fact that he comes back year after year and still produces top-level bowls is remarkable.  I have huge admiration for Andy – he's a credit to the sport."

After the earlier match, Alex Marshall – who partnered Foster to World Pairs success earlier in the week for the first time – conceded that his opponent had been unfortunate in the first tie-break end:  "Rob was unlucky that his first shot bowl landed in the seam of the carpet – and his two later perfectly-weighted deliveries just didn't nudge the original bowl nearer the jack to hold the shot.

"I threw away the first set – his first few ends were brilliant," continued the 43-year-old from East Lothian after his 7-8, 9-1, 2-0 win.

"It's great to be in the semis – it's always good to be here at the end."

Weale felt he had started off well in the match.  "I got what I deserved by winning the first set.

"I was a bit unlucky in that first tie-break end," added the 47-year-old from Hereford who has won medals in six of seven appearances in the Commonwealth Games.  "My first bowl landed on the seam and reached it with my next two bowls - but it didn't move as I expected it to."

It was a confident performance by Greg Harlow that put the defending champion from Ely into the last four after beating English qualifier Brett Arkley.  The 45-year-old from Newcastle-upon-Tyne had claimed his first-time quarter-final berth after upsetting local hero Mervyn King, the 2006 champion from Norfolk.

But Harlow was too good for the Tyneside outsider, despatching Arkley 13-4, 10-6 to reach his fourth semi-final since 1997.

"Brett couldn't have had a tougher draw, first beating Billy Jackson, the 2009 champion, then Mervyn, champion three years before, and then coming up against me!  He did well to get this far," said the world No2

"I'm delighted with the win – I knew I was favourite, but never ever took anything for granted."

The final game of the day saw Suffolk's world No3 Mark Royal claim his first semi-final berth in the world championship after surviving a close contest with Scotland's 11th seed Darren Burnett.

After leading the first set with two ends to go, Royal conceded a surprise four in the eighth end and, despite winning a single in the ninth, went behind as the Scot took the set.  The 36-year-old from Stowmarket swooped back to draw level – then clinched the first two ends of the tie-break to secure his 7-8, 9-3, 2-0 victory.

"My first semi:  I'm very pleased," said the beaming left-hander.  "I was devastated to lose the first set – shell-shocked, in fact – but I'm fairly confident this week and kept my head down and came through OK."

RESULTS:    Potters Holidays World Indoor Bowls Championships, Hopton-on-Sea, England

World Singles, quarter-finals:
[4] Alex Marshall, MBE (SCO) bt [12] Robert Weale (WAL) 7-8, 9-1, 2-0
[1] Greg Harlow (ENG) bt [Q] Brett Arkley (ENG) 13-4, 10-6
[2] Paul Foster (SCO) bt [10] Andy Thomson (ENG) 7-6, 2-11, 2-1
[3] Mark Royal (ENG) bt [11] Darren Burnett (SCO) 7-8, 9-3, 2-0

Saturday (22 January) schedule:
12.30pm
World Singles, semi-finals:
[3] Mark Royal (ENG) v [2] Paul Foster (SCO)    
2.30pm
[1] Greg Harlow (ENG) v [4] Alex Marshall, MBE (SCO)    

Sunday (23 January) schedule:
2.00pm
World Singles Final
Harlow or Marshall v Royal or Foster