|Stop that pigeon ... err ... man!|
The standard British Army revolver round until the adoption of .380/200 and 9mm Parabellum. The .455 fired a fucking huge 265 grain bullet which was about the same size as a steam locomotive and had roughly the same effect when it it hit something.
British officers concerned about their personal safety were not fully satisfied even with this and used to buy cylindrical 'Manstopper' bullets which had an even more catastrophic effect on any unfortunate sweaty native foolish enough to give them a dirty look or pinch their wife's bottom. Alas, German soldiers taking British officers prisoner in 1914 found some of these, deemed them somewhat 'unsporting' for use against fellow white men and court-martial ensued.
In the 1920s the decision was taken that something a little lighter would be more appropriate, bearing in mind how rarely handguns were actually used in combat, and the .380/200 round was adopted along with the Enfield No.2 Revolver, a scaled down version of the Webley Mk VI.
Anoraks hugely enlarged here