I found this anecdote in Harry Plunket Greene’s  witty biography (portrait) of Charles Villiers Stanford. It is largely self-explanatory.
Plunket Greene wrote: [Stanford’s] criticisms were expressed in various ways, mostly unpremeditated, and many of them are delightedly quoted by the recipients to this day. He was devoted to C. S. Lang,  now Director of Music at Christ's Hospital. It was Stanford's custom when his work was over at the R.C.M. to take a taxi to the Savile Club  in Piccadilly, but one day he received orders from his doctor to walk the distance for the sake of exercise. Lang, having heard of this, used to wait for him on the steps to see that he obeyed instructions. He [Lang] told me that one morning he turned up at his lesson with a superb (as he thought) six-part Motet, a setting of Dominus Illuminatio Mea . Stanford looked at it for a minute or two, threw it on top of the piano and started in on the Dorian mode or some other remote subject; he never mentioned the masterpiece. In the afternoon, they walked together to the Savile. There is an undertaker's shop in Knightsbridge and as they passed the door Stanford gave him a shove and said:
'Take it in there, me boy.'
That was the only reference he ever made to it.
 Harry Plunket Greene (1865-1936) was a hugely popular Irish baritone and fly-fishing enthusiast. He was the baritone soloist in the premiere of Edward Elgar’s The Dream of Gerontius. Greene was also the son-in-law of Charles Hubert Hastings Parry. In 1935, he published what was for many years the only biographical study of Charles Villiers Stanford.
 Craig Sellar Lang (C.S.) (1891-1971) combined composition with an academic career. He was Director of Music at Christ’s Hospital School in Sussex between 1929 and 1945. His best-known composition is Tuba Tune in D major, op.15 which is often heard in cathedrals, parish churches and on CD.
 The Savile Club is a traditional London gentlemen's club founded in 1868. Until 1927, it was located at 107 Piccadilly, though it has subsequently moved to 69 Brook Street. Many eminent composers and musicians were members including Edward Elgar, Hubert Parry and Adrian Boult.
 Dominus Illuminatio Mea trans. The Lord is my Light.