Roland Perry gurgled happily, sounding much like they
were saying:

Of course, first you have to realise they are a vicar, or that the
vehicle is an ambulance on call.

As with vicars - except more so - ambulances on call tend to have some
rather unsubtle clues visually identifying them.

In this case, the people on the day seem to accept that the ambulance
(an estate car) wasn't as recognisable as you assume.

Have you actually read the 137 page PDF containing the statements?