When Walter left to go to America, Hans Knappertsbusch was appointed to the job and immediately terminated the employment of any non-Germans working for the company.
In 1931 Braithwaite joined the Vic-Wells, later the Sadler's Wells Opera Company, the company run by the fiercely autocratic Lilian Baylis, who persuaded the politicians Winston Churchill and Stanley Baldwin, the writers G. K. Chesterton and John Galsworthy, the composer Ethel Smyth, and the conductor Thomas Beecham to raise funds for a new theatre at Sadler's Wells in Islington, where there had been a theatre since 1683.
The company performed not only opera, but ballet and theatre as well: among its stars were Laurence Olivier, John Gielgud, Margot Fonteyn, Robert Helpmann, Joan Cross, Constant Lambert.
Braithwaite conducted Wagner's Mastersingers and Lohengrin Beethoven's Fidelio, the Mozart operas (including Cosi Fan Tutte, then rarely done), Verdi's Don Carlos and a highly successful Falstaff, the Puccini operas, and Ethel Smythe's The Wreckers.
London was set on fire by waves of German bombs, 430 people were killed and 1,600 badly injured.
During the war he was also much involved in the campaign to save the London Philharmonic Orchestra during these years and can be seen in the film Battle for Music, which documents that story.
After the war he joined the Royal Opera House, Covent Garden, as Music Director of the Ballet Company where he conducted the western premiere of Prokofiev's Cinderella with Moira Shearer in the title role.
His recording legacy is mainly as an accompanist to some of the greatest singers of the mid twentieth century – Elisabeth Schwarzkopf, Sena Jurinac, Kirsten Flagstad, Tito Gobbi, Nicola Rossi-Lemeni and Joan Hammond amongst others.
Also active as a composer, writing two operas (including The Pendragon, about King Arthur)[3] as well as a varied collection of other pieces Braithwaite wrote the book The Conductor's Art (ISBN 978-0313200588), published in 1952.