Three Tourists and One Local

He has a gun, a big hat, a red uniform and isn't smiling. The three girls have cameras and casual clothes. So guest who the tourists are.Incidentally, I'm not sure if the soldier is a Beefeater or not. I also don't know what he's guarding. Perhaps an important door? Or maybe he's just a tourist attraction. Kind of like the giant tortoises at Reptile Gardens?