Summary from a book:
In early 1941, the Admiralty asked Guy Maunsell to look at a problem in Liverpool Bay, German aircraft came from the direction of the Irish Sea, and were attacking Liverpool. In May 1941, in a space of 2 days, over 90000 tons of shipping were lost.
Tha answer was to be forts of 7 towers each, 4 for 3.75 inch HAA Guns, 1 for Bofors guns, 1 for a control tower, and 1 for a searchlight, connected by Catwalks.
The tops were 36 feet square, with 3 floors.
They placed an order for 38 towers, which was 5 forts and 3 spares. they were to be built by the "Cleveland Bridge and Engineering Co. Ltd at Bromborough. After construction had started, the Liverpool order was cut to 21 towers. The layout actually looked like the ground layout of a typical 4 3.75 inch HAA site on land.
The surplus parts and steel from Bromborough were sent down to Gravesend to be used on the Thames Forts.
Each tower had 3 floors, and an armour plated roof. Each had it's share of accomodation, and were insulated with hardboard. The floors were 3/4 inch Ashphalt.
The Bofors tower had the messing arrangements, and the Searchlight tower the 30KvA generator. The steel windows were made by Critall (still around ?). They were painted in 3 coats of bituminous grey paint. The first tower to be sunk was the Bofors tower, because it was self defending.
They were actually refurbished in 1950 at the start of the Korean war.
They (don't know which) appeared in :
Dangerman (Patrick Mooghan)
Dr Who and the Sea Serpents
a Video for "Flame".