The duo became the first team to win the pairs title for a third consecutive year, adding it to the outdoor equivalent they won in Adelaide six weeks ago.
Yesterday's final was an all-Scottish affair, against Stewart Anderson, from Auchinleck, and Arbroath's Darren Burnett and it was a tension-laden affair. Foster and Marshall took the first set 9-7 and Anderson and Burnett the second 8-7.
Marshall then drew the match-winner with the last delivery on the third and final end of the shoot-out.
It was a tale of Anderson's awesome drawing game against Marshall's conversion shots, and the match finally swung the way of the East Lothian man who continually demolished heads for maximum results.
Marshall admitted: "Winning 19 world titles is a huge honour for me. Tony Allcock and I had 18 from various international events so this one, particularly a third pairs in a row at Potters with Paul so soon after our success in Adelaide, is very special.
"Stewart was relentless. Paul has done that many times to other players but no-one really does that to Paul; he had to keep digging deep to and try to keep Stewart in check."
Foster said: "I wasn't on top of my game today – Stuart kept me in my place – but Alex and I play as a team and bounce off each other. I think the man thrives on the pressure; he showed that today."
"We could have won the first set but Alex played some really big bowls and got maximum results. A lot of pairs would have buckled but we hung in. I had a chance to take the shot bowl out on the second end of the tie-break and win the match. I should have hit the target but I missed."
Foster and Burnett come face-to-face again today in the final of the World Matchplay Mixed Pairs title. Foster is partnered by Laura Thomas from Wales while Burnett lines up alongside Karen Murphy, the Australian.
Before that, Anderson will take on another Scot, Alloa's Steven Allan, as play in the second round of the singles begins. Marshall plays his second-round tie against yet another Scot, David Gourlay, tonight, while Paisley's Jon Ross takes on the English qualifier, Pat Briscoe.
The final first-round tie yesterday produced another surprise as Anglo-Scot Andy Thomson, the defending champion, went down 8-8, 8-3 to Phil Bennett, a qualifier from New Zealand.