Absolutely real.
British law defines a "pistol" as a firearm with a barrel shorter than 30 cm (12 in) or a total length of less than 60 cm (24 in)[23] (this definition encompasses revolvers, revolving pistols). Only muzzle-loading pistols—including muzzle-loading revolvers—are permitted; in practice all such firearms use black powder—a Class 1 explosive—as the propellant. Small quantities of muzzle-loading pistols and revolvers in various calibres, which comply with the regulations, are manufactured.[24] All other pistols are mostly prohibited in Great Britain, with some exceptions such as pistols used for the humane dispatch of injured animals (such as deer) and some historical firearms.
This law created a new market for "long-barrelled revolvers" and "long-barrelled pistols", firearms with a permanently attached extension to the grip, making them long enough to fit under the legal definition of a rifle. Long-barrelled pistols in single-shot, or long-barrelled revolvers, both of any calibre, or semi-automatic in .22 rimfire, are all permitted with a Firearm Certificate.[25]