Patrick Macnee left Eton in 1939 and "determined to romp through the summer".

A short time after the outbreak of World War II in 1939, he attended an audition at the Webber School of Singing and Dramatic Art in Clareville Street, South Kensington, one of the leading drama schools in Britain. Patrick was accepted and awarded a scholarship at the school, moving into a single room at Roland Gardens in nearby Kensington.

At the school, which he attended for nine months, he was introduced to Barbara Douglas, a fellow student, whom he fell in love with. They became a couple and married in 1942, with Barbara becoming the mother of his two children, Rupert and Jenny.

Patrick made his professional stage debut as Gerald Forbes in the play When We Are Married at the St. Francis Theatre in Letchworth in the autumn of 1940, playing to audiences there for five days. During the following February, he played different roles in The Good Young Man by Kenneth Horne, The Squall by Jean Bart and Painted Sparrows by Guy Paxton and Edward V. Hoile, and this led to further work in May 1941 in Gilbert Nathan's Five Plays at the Comedy Theatre in London. The production opened during the Blitz, when London was subjected to terrifying air attacks by Germany’s Luftwaffe.

In July 1941 he was offered the role of Laurie in Little Women alongside his fiancée Barbara, who played the role of Jo. On 7th July 1941 the troupe started a successful tour of the United Kingdom, which began in Bradford and ended in London with engagements at the Westminster Theatre between December 22nd 1941 and February 7th 1942.

Patrick undertook several further plays during 1942, such as Once There Was Music and Romance in ‘A’ Flat, but his career was interrupted when his call-up papers arrived and he had to go to war. He left London in October 1942, only twenty years old, for naval training as an Ordinary Seaman to the North Wales coast, at Pwllheli Camp.