Well, its no beauty any more!:
But I bought this because of the patent number seen on the lug. It is 430296, which is shown (abstract only) here: espacenet - Bibliographic data
Its a 3-part case made - and patented - by Dennison in 1935. The key feature seems to have been that the lugs are integrated in the bezel - something later seen on a lot of low end British watches.
Alas, the dial and hands have been augmented with blobs of white paint - maybe luminous at one time - and is also badly marked.
The Swiss movement is marked 'Shield Sterling', which I can't find anything about. It is a 10''' (or thereabouts) 15J movement and has INCABLOC shock protection. Unless I'm mistaken, this must have been a very early example of its usage - particularly in a non-military watch. I can't identify the movement, nothing under the balance, which is running fine and keeping time.
Bought on a whim for £3.20.
Dennison's original premises: