Thanks for the reply. The parish register shows they were resident at 39 Warren Street at the time of the baptism, and James was already a Zinc Worker.
I came across one curious thing in the 1911 census. One of the sons of James D Butters (1838-1891) was Henry David Butters, who in turn had a son James David, born around 1906. The 1911 census shows two small boys called James Butters:
1. 5 year old James, born in Paddington, living in Paddington with his father, Henry.
2. A four year old James Butters, born in Kilburn and visiting the family of Hannah Cousins (nee Giles) in Wokingham, Buckinghamshire. Hannah's half sister, Emma Cummings was the wife of William J Butters, who was Henry's uncle, and they lived in Kilburn.
There seem to be no other people of that name born around then in London or Middlesex, so it is presumably the same boy. It seems odd, though, that he would be staying with such distant relatives, and not in the immediate vicinity.