On closer inspection I can see the spade-shaped ground hole. At first glance I thought it was the ground-pin sticking up on an upside-down French outlet. That'll teach me to look more closely in future!
TG, I can't imagine why you'd have something like the BS546 (socket #4) in a hospital there, unless it was installed for some special purpose. Could it have been the smaller 5A version? These 15A types are really huge!