The Shepherd Gate Clock is located on the outside-wall of the Royal Observatory in Greenwich, UK. It is a 24 hour electric clock and was probably the first clock to show Greenwich Mean Time to the public. The clock is known as a slave clock, displaying the time from the master clock inside the observatory. Signals are received from the master clock as electrical impulses.
The time on the clock was 16:45 (GMT time), but the time on my watch was 17:45 (BST - British Summer Time). Talking about BST, the clocks will go back the GMT time on Sunday 30th October.