Green’s Dictionary of Slang

Captain Copperthorne’s crew n.

[? the inadequacies of some long-vanished officer]

(orig. naut.) a group or team without a stated hierarchy, where everyone concerned wishes to lead.

[UK]Grose Classical Dict. of the Vulgar Tongue n.p.: Captain copperthorne’s crew, all officers; a saying of a company where every one strives to rule.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.