I met DB on two occasions and can confirm he was not a very nice bloke at all. However, these 'qualities' enabled him to achieve what he did, which is remarkable.
I asked him for an autograph (on this occasion I was a 14 year old ATC cadet and was assisting at a B of B airshow in the early 70's) and his comment was a loud 'that bugger Johnson's got there first!!!' refering to another signature (on an RAF recruiting brochure) from another famous ace (and much nicer chap) AVM 'Johnnie' Johnson. He did sign, but then made sure he did not stay to answer any questions, unlike AVM Johnson, who was a real gent.