By the beginning of World War II, over 70 12-metres have been built. Two big British fleet existed, in the Solent and on the East Coast, based in Essex and Suffolk. Across the Atlantic there was a growing fleet at Newport, designed by magical names as Herreshof, Burgess and Stephens. The new world had enthusiastically taken up this European concept and thrown American technology at it. New construction methods and radical rig and deck fittings began to appear. The US was making the running although meetings between the two fleets were rare.

With the end of the war came the realisation that the days of the J-class dinosaurs were over. The 12-metre was the chosen class when the America's Cup resumed in 1958.

It was the beginning of the Twelves' finest hour.