My paramedic daughter can flesh out that statement: because A&E is understaffed / busy they quite regularly cannot make anyone available to accept the incoming patient. The ambulance crew remain responsible for their patient and his/her welfare until the handover can take place - at times for up to an hour. Meanwhile the ambulance and crew are unable to accept any calls. In South Cumbria there are a small number of ambulances and there are times when they are all parked at A&E awaiting patient handover. Any cover for South Lakeland then has to come from the North of the County - 50 to 75 miles away from our 'local' A&E. Which is in Lancaster. Unless the patient needing A&E is a heart attack case in which case it is at Blackpool - a further 30 miles away.This is not to defend the ambulance /paramedics but as soon as you got to the point about being at A and E and there were crews chatting.
I do remember recently that, whilst at hospital, I noticed a couple of crews around and I was told that because of procedures and H and E, a lot of patients who are brought in by ambulance, then the crew that brings them in has to stay till they are admitted or discharged. Apparently, long gone are the days when there was a patient brought in, dropped off etc and the crew going out for another emergency. That's one if the reasons patients brought in by ambulance are priority but personally a waste of valuable time and resources but not the ambulance staff fault. Course, at that time it could also have been shift change or break period but on arrival to hospital, the system was also quieter for the need of ambulances. I don't suppose anyone would approach an ambulance person and say that 999 say you're very busy but there are X number of crews here? I wouldn't but some people would.