Certainly when I was on my TWU course at Brawdy in 1976, St. Davids was our 'crash' diversion. We had a brief on the place, which seemed to consist of landing, turning off and finding somewhere to park on a first-come, first-served basis - I can't remember whether there was any Air Traffic Control there, or whether we were supposed to land non-radio.
Fortunately the only time I had to divert was to St. Athan shortly after take-off when the late 'Puddy' Catt (flying as #2), returned with an engine snag, only to take his Hunter and the barrier almost into Pen-y-Cwm post office.