UK: Mosley defeats Chamberlain in the 1924 election and becomes the rising star of the Labour Party, initially on the left but gradually shifting towards a "third way" position.
In the early 30s he becomes leader of the Labour Party after the left-wing breaks off, and leads Labour to victory forming a minority government. In order to form an effective government he forms a national unity government with sympathetic elements within the Liberal and Conservative parties willing to support his sweeping reforms to deal with the depression, based on Keynsian economics, Imperial Preference, corporatism and rearmament.
Opposed on the left by the Popular Front (left-Labour, Communists, Independent Socialists and left-Liberals), and on the rights by an alliance of dissident Liberals and Conservatives led by Churchill, the national government is fairly unstable.
Eventually the Popular Front attempt to organise a general strike with the aim of bringing the government down and calling fresh elections. Fearing the possibility of a Communist uprising (and also seeing an opportunity to secure his power), Mosley orders a violent crackdown on the strikers and pushes through sweeping emergency powers, with the full backing of the establishment.
With the left suppressed, he then turns on the right. With his opposition cowed into submission the members of the National Government are merged into a New Party that will govern the British state. Thus begins the era of British Fascism!