It can be difficult to tell in England where show and ceremony end and actual function begins, but in this case it's a little bit of both. A detachment of the unit providing the Queen's Guard at Buckingham Palace still mounts a guard at the Tower. This soldier is standing guard near the entrance to Waterloo Barracks, the home of the Crown Jewels. I am assured by the Yeoman Warders that the rifle is much more than decorative or ceremonial.