But the bid was a two-way move, showing either 10-12 points or more than 16.
South's one-no-trump response was natural, showing 8 to 13 points or an unlikely 16-plus.
He opened in third position with one no-trump, the weak variety showing 12 to 14 points.
West's double showed at least six high-card points, and was not for penalties.
If this is not available as an invitational bid to show 11 points, the partnership will have trouble.
But since one club would have shown at least 16 points, North had to open with one diamond.
South has shown 16-18 total points, while North's hand is largely unknown.
"It's clear," he said then, and showed me two points, on opposite walls, at a man's height.
The film shows two different points of views on this issue.
South's double over two spades showed 14 or 15 points.