The vessel in the foreground of #20 is the bucket dredger Foremost 48, registered in London, built in 1929.
I am occasionally asked about the aerial ropeway by people on my ship because you can still see the concrete bases of the support masts at intervals along the Eastern Arm and also the two blocked off tunnel entrances in the cliff face in line with the Eastern Arm.
This dramatic Pathé film clip shows the 5,000 ton bunker on the end of the Eastern Arm and the aerial ropeway whilst under attack by the Luftwaffe in 1940:
http://www.britishpathe.com/record.php?id=25833