The choir under Thomas Armstrong (seated centre).

Thomas Armstrong (1898-1994), later Sir Thomas, and Principal of the Royal Academy of Music 1955-68.

From 1928 to 1933 he was organist of Exeter Cathedral, a post he held in tandem with the directorship of music at the University College of the South West.

The exact date of the photo is uncertain. The original is in Exeter Cathedral Archive.

It was taken in the Bishop's Palace garden, with the palace and then the cathedral behind the choir.

With thanks to Tony Goldsworthy, who provided this information in January 2020:

One of the trebles of Armstrong's choir was Robert Knill Goldsworthy (b. 1914), Tony's father. He was a chorister from, Tony believes, 1920 to 1928. He died in 2010 at the age of 96 yrs.