Waterlow's wife Mary was the daughter of John Hill, banker of West Smithfield and was born about 1853 in Highbury. In 1881 they were living in Willesden, London.
A wholesale stationer, and member of the Stationers Club from 1867, he became Master Warden in 1873; he also became a member of the Liberty of the Butchers' Company in 1880. He joined the City Liberal Club and became Sherriff of London and Middlesex in 1880. It was probably in his official capacity that Whistler had dealings with him.
He was a broad churchman, a Member of the Honorary Artillery Company, and of several choral and musical societies, a leading spirit of the Moray Minstrels and President of the Philharmonic Society of Brondesbury. Waterlow was also on the board of Management of the London Orphan Asylum at Watford.
UK census 1881, from http://www.familysearch.org (accessed 2004); Crook, J. Mordaunt, The Rise of the Nouveaux Riches; Style and Status in Victorian and Edwardian Architecture, London, 1999.