Not a complete myth surely? As I understand it, that was pretty-much the standard means of delivery for Red Beard. I assume the practise didn't last very long as Red Beard didn't either. Tony Blackman describes "half loop" manoeuvres in his book quite graphically.
I did say below that the public "aerobatics" (ie- rolls) were not performed by service pilots but only by Avro pilots. Some RAF pilots did it but the RAF put a stop to it and asked Avro to do the same. Ironically, when the request was made, Jimmy H had just flown another barrel roll over Finningley during a visit. Avro did stop rolling and half-looping the Vulcan in public after that, but I know from first-hand interviews that aerobatics still continued away from public scrutiny, chiefly for the amusement of the crews. The rear crew didn't seem to object, in fact one regular Avro flight observer claims that he used to eat his sandwiches while such antics were being performed!