Bullmastiffs have been bred mainly for pets and the show circuit for quite a few generations, 20 years ago i had two that would guard well and liked to come out with the 3/4 greyhound 1/4 whippet, they had a strong prey drive but were very disobedient and not allways under control, they both did well in the showring also as youngsters but eventually the dog started curling his lip at the judges, end of show carreer for them and me as i lost interest in showing.
Today they can make a good pet and family orientated deterrent.
True guard dogs need to be fit intelligent and above all in this da