E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Briton (Like a).
Vigorously, perseveringly. To fight like a Briton is to fight with indomitable courage. To work like a Briton is to work hard and perseveringly. Certainly, without the slightest flattery, dogged courage and perseverance are the strong characteristics of John Bull. A similar phrase is To fight like a Trojan.