In a reversal of fortunes, former world champion Ian Williams went crashing out of the Stena Cup in Sweden while the man he so proudly beat in the pool stage, America's Cup skipper and triple Olympic gold medallist, walloped the current tour leader Mathieu Richard of France to go through to the semi-finals.
Williams, courtesy of topping his group in the early rounds, also win the right to choose his opponent in the best of five quarter final. He picked Sweden's Magnus Holmberg but on the course in Marstrand Harbour went down 1-3, one of the losses due to a penalty.
Ainslie stormed through 3-0 and found time to praise the tactical input of fellow gold medallist Iain Percy as the wind turned light.
In the women's division, the British trio of Lucy Macgregor, sister Kate and Annie Lush made short work of their quarter final against Lotte Meldegaard Pedersen of Denmark and, as top scorer, picked Renee Groenevald of The Netherlands as her semi-final opponent. In the other semi, Ekaterina Skudina of Russia lines up against Australia's Katie Pellew (Spithill).