Benchmark

I spent several months as a research student tracking down Ordnance Survey benchmarks and resurveying them. In theory they are good reference points for height, cut into buildings and posts, but they tend to move as structures are repaired. 
This one is right outside my house, and I never noticed it before; this is described by the OS as STO GTP FENCE CORNER SW SIDE RD NW FACE, and was last verified in 1957, at 184.526m above sea level. Who knew?