They range in size from some just a couple of feet long to 11ft monsters of several tons which would have fired solid iron shot weighing 42lb each. Most are bought at auction or from other enthusiasts - although there are only a handful of serious collectors in the country.
Mr Walker, whose collection now numbers nearly 50 guns dating from about 1710 through to the 1890s, says: "I have always been interested in ordnance, but it really started 13 years ago when I saw a pair of guns advertised for sale in the local paper. They were about 4ft long and had been outside a cottage in Bembridge on the Isle of Wight for about 200 years."
Gun barrels used as street furniture are another source. As roads are widened and streets pedestrianised, Mr Walker rescues the guns embedded years ago as bollards in pavements.
Pride of the collection is a rare 1848 smooth-bore Monk B ship's gun, probably the only surviving example, which Mr Walker estimates would be worth thousands of pounds at auction.
As well as the guns, Mr Walker, who works for an industrial security company, has examples of most of the ammunition used, including cannon balls, shells, bar-shot, chain-shot (used for destroying sails and rigging) and grapeshot.
His most recent acquisition is a Victorian mountain gun, which dismantles so that it can be transported by mule. Mr Walker now has his sights set on "some very, very big stuff" - a 38-ton coastal defence gun in fact - but worries that his garden is getting rather cluttered.Reuse content