If you would care to read the reviews of The long Good Friday, you will see that it was lauded to the skies as a superb film, one reviewer at the time questioned why it wasn`t distributed around more Cinemas, most of the other reviews had it as the best gangster movie of all time, some praise, in 1978 when the film was finished the IRA campaign was at it`s height,and as the film portrayed the IRA as coming out on top, hat didn`t go down well with the Brit establishment.
Dave why castigate Mirren when you are losing out, take my word for it, brutality and violence had nothing to do with the cinemas not taking the film, there were films around at that time which made TLGF look tame.