Green’s Dictionary of Slang

an officer of the NSPCC or RSPCA.

1954		D.V. Donnison Neglected Child 82: Workers [...] had been shut out of houses by people who suspected they had ‘put the cruelty man on to them’ .
1958		Sun. Express (London) 27 Apr. 6/6: The Cruelty Man has been asking questions about Janie.
1979		B. Whyte Yellow on the Broom 10: The gentry would send a policeman, or, worse still, a Cruelty man.
2001		Irish Echo.com.au 10–23 May XIV:10 🌐 He remembers living under the threat of being taken away in ‘the cruelty man’s’ big black car.
a.2003		J. Cairney ‘Nostalgia for a Tenement’ [poem] The Cruelty man, the School Board, all the men that came to the door / The Rent man, the Gas man, the man from the Co-op store.