Armstrong was born in in . His father was a clergyman and Armstrong was educated at in London.
Armstrong held his first solo exhibition in 1928 at the in London. In 1933 he joined and displayed a set of semi-abstract paintings at their one, extended, exhibition. Throughout the 1930s Armstrong continued to work as a designer as he also continued to develop his art. He produced a number of remarkable posters for and also produced four posters for the . Armstrong designed a number of book covers for the , including for 's Sado published in 1931. He worked on the first production of the ballet and on a number of 's film productions, designing costumes for , and
Newlands Corner is a 103-hectare (250-acre) nature reserve east of Guildford in Surrey. It is owned by the Albury Estate managed by the Surrey Wildlife Trust under an access agreement between the estate and Surrey County Council.