At 20 he was back in London and signed a contract with Ascherberg, Hopwood, & Crew as a songwriter. The outbreak of the First World War a year later was to set in motion Novello's adult career as a songwriter, as he generated a string of patriotic and morale-boosting songs that were embraced by the public, most notably "Keep the Home Fires Burning." By 1916 Novello himself was in uniform as a sub-lieutenant in the Royal Naval Air Service, but he kept writing songs, now for London stage shows. His songs became highlights of some of the most successful shows of the period, and amid this flurry of stage composition, Novello also found room to embark on an acting career in both European and Hollywood movies, and on-stage in London, and quickly established himself as a popular matinee idol. By 1921, he'd extended his acting career to Hollywood. It was during this same period that he had his first professional contact with Jack Buchanan, when he composed "And Her Mother Came Too" for him in the stage revue A-to-Z. Novello was equally known in America during the 1920s as a composer and screen actor, in movies such as The Bohemian Girl, The White Rose, The Constant Nymph, and The Vortex. His most enduringly important screen performance, however, was in The Lodger (1926), directed by Alfred Hitchcock, which was the director's first thriller, his first important movie, and his first hit, and remains one of the most widely known of British silent films.

Novello's main interest was the stage, and he was never willing or able to tear himself too far away from live theater. Amid his songwriting and acting, however, he was spread thinly enough during the 1920s so that he came rather late to the writing of complete shows, which ultimately proved the wellspring for his greatest successes. He emerged, rather suddenly, with a hit of what were then serious proportions -- 243 performances -- in Glamorous Night (1935). The latter featured American-born soprano Mary Ellis, who was to be associated with most of his work over the next decade. He had an even bigger hit the following year with Careless Rapture, which ran for 296 performances, followed by a national tour that lasted for much of the next year.

Novello was the toast of London's theater community, and he occupied a very unusual position socially across the remaining two decades of his life. At the time, homosexuality was a crime that was subject to prosecution in England, and the theatrical world was among the few respectable social strata in England that afforded any sort of open tolerance or protection to the gay community, within the limits of reasonable discretion; figures such as Noël Coward and Terence Rattigan, to name just two of the more celebrated theatrical talents of the period, were officially closeted but comfortable within these boundaries -- but Novello was so popular a figure that his sexual orientation was virtually an open secret far beyond the ranks of theater people. Shockingly, almost heartbreakingly handsome in his younger days and even into middle age, he could make women swoon openly and gay men swoon quietly as a silent screen figure, and his lovers among the latter included a number of extremely famous literary and performing figures of the period (and, it has been suggested, at least one highly placed political figure).

Novello's role in his first two shows had been as a composer, but The Dancing Years (1939) brought him back as a performer alongside Ellis, in what was one of the last great London stage hits before the outbreak of World War II. The show was practically a Novello hits collection, and ran 187 performances, ending in September of 1939; it was revived three years later and ran for just under 1,000 performances, an extraordinary achievement but an understandable one, as a welcome piece of highly melodic and comforting nostalgia in the depths of the war years. It was also filmed in 1949 by director Harold French, with Dennis Price and Giselle Preville as the two leads. These shows were throwbacks to the kind of operetta-based works that dominated English theater in the early years of the 20th century. They were more Viennese in character than British; Novello was part of a tradition that encompassed the likes of Franz Lehar and Emmerich Kalman.

Arc de Triumphe (1943) was another hit for Novello and Ellis, though it was never as enduring, musically or commercially, as the shows that preceded or followed it. Novello had the biggest hit of his career in 1945 with Perchance to Dream, which ran for over 1,000 performances over the next three years. This production was a double triumph for Novello as it used his own libretto. In 1949, Novello and librettist Christopher Hassall delivered King's Rhapsody, a Ruritanian romance that, in addition to such operetta-based pieces as "The Violin Began to Play" and "Someday My Heart Will Awake," contained an extended orchestral showpiece that reflected some of the developments that had overtaken theater in the previous decade. Novello was part of the cast as well and remained with the show until his sudden death, from coronary thrombosis, on March 6, 1951. He was replaced in the cast by none other than Jack Buchanan, for whom he'd written "And Her Mother Came Too" 29 years before.

Novello's recognition and reputation long outlived him, even if his music didn't endure as long -- even during his lifetime, music was changing faster than his own style of writing was evolving, and in the years and decades after his death the London stage would be transformed in ways that Novello would scarcely have recognized. But the Ivor Novello Award, given by the British Academy of Composers and Songwriters, has become one of the most coveted and respected entertainment honors in England, given to songwriters and arrangers of exceptional merit. Recipients have included Ian Anderson, Stanley Black, Lou Reed, Mick Jagger and Keith Richards, Justin Hayward, John Lennon and Paul McCartney, Kenny Gamble and Leon Huff, Jeff Lynne, Freddie Mercury, David Bowie, Barry Gibb, Robin Gibb, and Maurice Gibb, and Joe Meek.