Is it or is it not thats the question

Interesting question there Stevo I can see why CT web site says that about HP, but for me it looks too narrow and the construction of the ground floor is completely different, the two brick colums are clearly load bearing supporting that lintol whereas the 'fort' does not need this because its roof slab is also the window lintol, its all cast as the same RC slab if you see what I mean, so that it is possible to have continious window glazing across the front elevation as well as a return on either side. The width of a fort ground floor externally is 24 ft 10 in. My first thought was that despite the presence of the spiral stair case that this is not an adapted fort but it might be! Neither is Treblezue which off course is an austerity satellite airfield and would'nt have had one for that reason. Getting back to HP, if you wanted to adapt a fort ie remove the tower section and build a wider one, you would not really want to structurally alter the watch office roof slab in such away as to completely re-build it (cut out the lintol section then make it good in order to install another lintol for small windows - it does not make sense it would almost be be quicker and easier to build a brand new building). Unless off course an aeroplane had taxied into the front section, thus destroying the original lintol. Well that my view.

Stevo your quite correct about Turnhouse, back in 1994 I was unsure but perfectly clear now that it is the same as Hornchurch ie built without tower.

The H P building is a mystery, I still think this is not the building but something else built c.1943.