The South Foreland Lighthouse was used by Guglielmo Marconi during his work on radio waves, receiving the first ship-to-shore message from the East Goodwin lightship, the first ship-to-shore distress message (when a steamship ran into the same lightship, and the lighthouse relayed the message up the coast to the Walmer lifeboat), and the first international transmission (from Wimereux, France, in 1899).
Originally there was another lighthouse further down towards the cliff edge to give a bearing on the leading lights principle when a ship was at the point where it could safely turn left into the Downs behind the sands or right to go safely around the Sands. They were both built in the 1840s. However, the Sands shifted over the following years until this bearing became dangerously inaccurate and so the lower light was taken out of service in 1910. It still survives as part of a private garden but is under threat from cliff erosion.
A view of the South Foreland Lighthouse, overlooking the Dover Cliffs
A drawing of the South Foreland Lighthouse
And, just because I like it: A postcard showing the western docks of Dover Harbour