Not sure the ability to do a barrel role was within the design spec’s as such – has no value as a tactical manoeuvre for a large bomber. I think it was the Avro test pilot getting a bit frisky one year at a Farnborough airshow, and I seem to recall from a documentary that he got a bit of a bollocking for it. I think he only did it once or twice. In anycase in theory any aircraft is capable of doing a barrel role so long as +ve G is maintained. Someone did a barrel roll in Concorde once and it certainly was not in that aircraft’s design spec’s.
I have fond memories of the Vulcans and Nimrods. I was an Apprentice at BAe Woodford and lived under the flightpath of the aerodrome as a kid when the Nimrods and Vulcans were there for refits, so became very used to seeing them flying over routinely. As an apprentice i heard lots of stories from some of the guys who worked on them. Seems strange when you see a Vulcan flying now and i’ve forgotten how commonplace it was.
One of the benefits of being an Apprentice there was bunking off my block release college course and going on-site and sitting on a grass verge next to the runway during the week ahead of the Woodford Airshow and watching all the aircraft practicing their display’s. I often saw them do things they would not be allowed to do during a public display as there was always a lot of competition between the pilots from different airforces and countries. The Vulcans and Nimrods easily put on some of the most impressive displays even compared to the fighters, all of which had their wings severely clipped apart from the Russians. The SU27 Flankers always stole the show, but seeing a Vulcan pulling off some fighter like manoeuvres was always an impressive sight. Also the sheer noise and vibration from their engines, you could feel your internal organs vibrate when a vulcan came round on a low speed bank, to flatten out and haul the nose up to almost stand the thing on its tail and climb out. I fear the good old days of airshows of that caliber are long gone.