These aren't cranes but were obviously a major feature of Dover harbour during the war.
Positioned on the Eastern arm of the harbour, they are part of an aerial ropeway system that ran from Tilmanstone Colliery. Part-opened in 1929, this section on the harbour wall in 1930, it was in use until World War Two although it wasn't used much after 1935. Becoming redundant at the outbreak of the war, it was eventually dismantled in 1954.
Running from the hopper along the harbour wall it entered into the cliff in two parallel tunnels, seen as black dots on the first picture.
I imagine that the wires and buckets were taken off when the war started, although I don't know for sure. It would certainly add to the realism to have the pylons on the wall, and provide a few more obstructions for low-flying aircraft!
All pictures taken from 'South Coast Railways - Dover to Ramsgate' by Vic Mitchell and Keith Smith.
Looking back towards the cliffs.
The height of the pylons can be judged from this pic. I reckon that there must have been about 12 pylons on the wall.
The coal hopper at the end of the ropeway. Pics 2 and 3 are adjacent.
The book also has a picture of the 'Piecemaker' railway gun and the railway tracks for the guns above St Margarets Bay if anyone is interested.
