The Matchless G9 and corresponding AJS Model 20 were launched at the post-war Earls Court motorcycle show in late 1948.

Initially for export to the US, it was not until the late summer of 1949 that the first examples reached the home market.

The styling was modern, and the dual seat, megaphone silencers, and bright chrome finish justified the name of Super Clubman for the Matchless and Spring Twin for the AJS.

In 1951, the rear suspension was upgraded to the Jampot unit, derided for its shape in the 28 September issue of The Motor Cycle magazine.

In the same year, minor changes included a new Lucas horn-push on the handlebar and a medallion badge in place of the previously used transfer.