Singer and tenor saxophone player Les Allen was born in England in about 1903 and emigrated to Canada with his family as a child (3 years old). Following in his father's footsteps, he learnt the clarinet and later the saxophone, being one of the first musicians to play the latter in Canada. He played for well-known Canadian bandleaders Burton Till and Luigi Romanelli. By 1922, though, he was struggling to make a living and nearly gave up the business. In 1924, Hal Swain recruited a band, including Allen, to travel to England. They had hoped to play at Rector's club in London, but found it closed. Luckily, they landed a job at the "New Princes" restaurant, and a Columbia recording contract. Swain preferred to sing the vocal choruses himself, but he obviously recognised a budding vocalist in Allen, and they sang duets together. The only solo vocal recorded by Les Allen was on  "I Love My Baby" - Columbia 3929 on the band's last recording session in February 1926. This is likely to have been because Swain had left the band by this time. There was some disagreement between Swain and others at this time which resulted in the forthcoming European tour by the band being under the leadership of banjoist Dave Caplan. On returning to England, Les Allen joined Alfredo's band, playing tenor sax and singing. This was sometime in 1927. Ironically, Hal Swain often joined in on the recordings to start with, maybe as a returned favour to Alfredo (Both bands had been at the New Prince's restaurant). During his time with Alfredo, he developed his vocal skills considerably and in Early 1929 formed a vocal trio rather ambitiously called "The Original Whoopee Boys" with Americans Phil Arnold and Eddie Brandt. When Arnold left to return to the States in July 1929, he was replaced by Eric Linden until the act broke up in late 1929. Judging by his recordings, a suggested timeline would be:
New Princes Toronto Band                                     November 1924 - early 1927
Alfredo and his Band                                              Early 1927 - Late 1929
Piccadilly Players / Sid Bright & his Band              Late 1929 - September 1930
Duets with Al Bowlly (variety act?)                         November 1930 - March 1931
Hal Swain and his Band                                         June 1931 - December 1931
Freelance?                                                             January 1932 - October 1932
Henry Hall's B.B.C. Dance Orch                              October 1932 - September 1934
In Rust/Forbes' discography he is also shown as playing for Jack Harris  from March to November 1928, but he did not sing at all with the band and I can't see him being able to do this as well as play with Alfredo. A puzzle!
During the late 1930 - early 1931 period, Les records a lot of duets with Al Bowlly, often with Len Fillis Hawaiian groups which makes me wonder if they didn't all tour together as a variety act. Also noticable is the amount of freelance recording work (singing) Les did in the year up to joining Henry Hall; and how little he was able to do AFTER joining Hall.
After Leaving Henry Hall, Les toured as a solo act, often topping the bill, and had great success with his recording of "Little Man You've Had A Busy Day" on which his wife, Anne and son, Norman had speaking parts. He also made a film "Heat Wave" at Gainsborough Studios. In 1935, pianist Laurie Day returned from Canada to be his accompanist. In 1937, Les formed a vocal group called his "Canadian Bachelors" and they were all genuine Canadians (though not necessarily bachelors): Jack Curtis, Herbie King & Cy Mack. After the war, he played the juvenile lead in a revival of "Miss Hook of Holland" before returning to Canada in 1948, where his started a second career in the office supply trade, retiring in 1971. 
References: "Voices in the Air" by Chris Hayes (1995).

Les Allen