Answer: a gun that sits on the North Terrace of Windsor Castle, pointing towards Eton College, the old school of Princes William and Harry.
A nearby plaque records it was part of the armament of HMS Lutine, lost off the coast of Holland on Oct 9 1799. The wreck was later handed over by the Dutch government to Lloyds, where the treasure it had been carrying was insured. The gun and the ship’s bell – along with some of the gold - were salvaged many decades later. The bell now hangs from the rostrum at Lloyds of London and is still rung: once for bad news, twice for good. Presumably Lloyds didn’t need the gun, which was rather the worse for wear after almost a century underwater. So it was presented to Queen Victoria and to this day decorates Windsor Castle’s North Terrace, once described as “the noblest walk in Europe”.