From their teens to early twenties, Mosley and his brother were involved with their father's post-war party, the far-right Union Movement (UM), which advocated for European nationalism as its core issue. Trevor Grundy, a central figure in the UM's Youth Movement, writes of the 16-year-old Mosley painting the flash and circle symbol on walls in London on the night of the Soviet Union's invasion of Hungary (4 November 1956). The flash and circle was used by both the UM and the pre-war BUF. He also says Mosley organised a couple of large parties as a way "to get in with lively, ordinary, normal young people, girls as well as boys, and attract them to the Movement by showing that we were like them and didn't go on about Hitler and Mussolini, Franco and British Fascism all the time". Mosley met his future wife Jean at such a party. Mosley and Alexander were photographed posing as Teddy Boys in Notting Hill during the 1958 race riots between Afro-Caribbeans and local white gangs of Teddy Boys. The following year, they canvassed for their father when he ran as a Union Movement candidate for the nearby Kensington North seat in the 1959 general election.