The Webley line of pistols served the British Army officially since 1887, but unofficially since the 1870's, as then British Officers were expected to supply their own pistols.  The Webley Mk VI was developed during WWI and was accepted in 1915 as the official British sidearm.  This robust design differed from the Mk V by having a squared off target style grip as opposed to the bird's beak grip, the foresight was screwed to the barrel instead of being forged with the barrel, and the barrel itself was lengthened to six inches.

Weighing 2 and a half pounds, with another pound for the bullets, the pistol was no lightweight.  Strong and durable, the Mk. VI served the British Army till 1947, which is amazing since they haven't been any new ones since 1923.  To the British Army's detriment, it is obvious that there wasn't much range time allowed or the pistols would have long since worn out. The break open action allows for quick reloads.

This .455 Webley, like most of the one's before it, relied on 45 caliber cartridges, which were proven manstoppers.  The slow fat bullet traveled at 650 ft/sec and the lead weighed 265 grains.  The bullet was still hollow at the base, a throwback to the muzzle loading era, but due to the design of the pistol, non hollow base bullets aren't as accurate.  Shooters of Webleys converted to .45 acp can attest to that

Accessories for the Mk VI included a bayonet, which was adapted from a French Gras bayonet, and built by W.W. Greener.  Designed by a Lt. Arthur Pritchard, they were made available by Greener for officers during WWI, but they were not issued. A shoulder stock was also available, which also fit Webley's signal pistols.

Webley shoulder stock

Most Webleys imported into the states have had their cylinders shaved to accept .45 auto on clips.  This works well, but accuracy suffers somewhat, however in close combat, who cares.  You  won't miss.  By WW2 the Brits had dropped their obsession with manstopping bullets by replacing the .455 with the new .38/200 bullet in a smaller frame gun.  The .38/200 is meatier than the .38 S&W, but who uses that round anyway.  They should have stuck to their .45's.

Views of a disassembled Webley

The following video is from DrakeGmbh's Channel on YouTube.  He demonstrates both the Prideaux speedloader and the Pritchard bayonet.