Geograph - photograph every grid square

Greenwich: 24-hour clock

The Shepherd 24-hour clock stands outside the entrance to the Royal Observatory. The minute hand operates as on a standard 12-hour clock, using the outer Arabic numerals, while the hour hand uses the 24 Roman numerals and revolves once per day.

Below it are public standards of length and (just visible in the bottom-right corner) an Ordnance Survey benchmark, at 46.31m above sea level.