London is where the Callum family lives. It appears that Dick goes to a boarding school, while Dorothea goes to a day school:
Dorothea had been seen off by her mother at Euston. Dick, coming straight from school, had joined the train at Crewe (PM2). At home Professor Callum had to be busy for a fortnight in London correcting examination papers .... (PM1).
At the beginning of Coot Club, Richard (Mrs Barrable's brother) had to go off to London to paint portraits of some important Indians .... (CC1)