Quite a few years ago now, a few of us had occasion to visit DAP in the old CAA House in Holborn. Whoever it was that escorted us told us about the misconception that x number of ATMs were the magic figure for qualifying for CAS. According to this person (& I can't remember who it was) when the department was set up, they were all chatting in a pub about what the criteria might possibly be for getting CAS and as part of the conversation, someone suggested a nominal number of ATMs which was (quote) "scribbled on the back of a fag packet"(unquote). It was apparently never actually adopted though. He didn't make it clear to us exactly what criteria were adopted, but I believe the inference was that each application was considered on its merits, taking into account the requirements of all airspace users in the area, & not just on the number of ATMs.
Those of our colleagues operating in very trying circumstances outside CAS have my sympathies, - from my comfortable position within the (relative) security of Class D!
RC