In the Second World War as the Allies were planning for D-Day and other missions they often put out pleas to the country for pictures and photographs of places of potential military importance: the coast of northern France was a favourite. People would send in their holiday snaps and the photographs would be collated to provide accurate knowledge of beaches and landing grounds. It was vital to the war effort.
Registering is a bit of a rigmarole and the confirmation step asks all sorts of questions that a novice to the site won’t know their preference for (forum sort order?). You also have the option to add your own home OS reference. I was casting my mind back to pre-GSCE geography (Where are you now Mrs Ambrose?) and recalled that Streetmap had an OS function. Off I trotted to get my reference and after several tries and tinkers I found they actually wanted the Landranger reference. Tsk.
It’s a fun site though and the photography is generally pretty good. It will also be an invaluable source of information for any future invasion of Britain.