I speculated whether WC had been to the South Kensington schools. He had. Here’s what GC says in his Autobiographical Notes, op cit.
I had an elder brother who had talent: he died young. My father encouraged us boys to draw, and used to take us to the British Museum, the National Gallery, and South Kensington Museum. [...]
We drew at an art-school in the evenings and often spent our half-holidays sketching; and though we took it as a matter of course that drawing was in some way to help us to get a living, the idea of painting pictures seemed to me as far away and unattainable as the moon! I had the old-fashioned idea that painting had to be learnt, and there was no prospect of that for us. My brother, in due time, worked under my father: later he gained a National Scholarship at South Kensington and became a decorative artist.
When I left school, at fifteen, I went daily to South Kensington Museum, and drew furniture, ironwork, Renaissance sculpture, etc., and attended the Art School in the evenings.
Soon there was a vacancy in the drawing office of the firm where my father was employed, and I was taken on.
GC in due course got his own scholarship, and attended South Kensington full-time from 1873 to 1875. I’ll say more about his studies on another occasion. William, being a year and a half older, was probably there a little earlier.
But whereas George was committed by 1876 to fine art, William, as we have seen, remained a decorative artist. He placed an ad appealing for work in The Times of 21 May 1877, while he was living in Fulham, perhaps newly-married: touching, this voice, in the competitive clamour and clangour of Victorian London, of a man who would die at only 31. You can see it here, surrounded by notices about cooks and governesses, with the word Clausen highlighted, and download the whole page, in all its unreformed typographical immensity, here.