Green’s Dictionary of Slang

1. the Law Courts in the Strand, London.

1898		W. Besant Orange Girl II 137: His cringing salute was almost as nauseous as the impudent brutality which he had shown in the Thieves’ Kitchen.
1909		(ref. to 1882) J. Ware Passing Eng. of the Victorian Era.

2. the Athenaeum Club, London.

1902		Chicago Trib. 2 Mar. 14/1: The ‘Thieves’ Kitchen’ has become one of the noted clubs of London. ‘Thieves’ Kitchen’ [...] is a popular name for the City Atheneum.
1937–84		Partridge DSUE (1984) 1219: —1923.

3. the Stock Exchange.

1977

D. Powis Signs of Crime 204: Thieves’ kitchen The Stock Exchange (taxi drivers’ slang).