Easily the best film in the Dick Barton trilogy, showing a cinematic professionalism the first two lacked. This was the last to be filmed but released second, sad to lose Don Stannard so young and promising in 1949. Apart from the Boys Own adventure storyline, and Barton speaking in capital letters, this was a good attempt at cheapo-noir, nice camera work and high production values being a constant source of surprise.
Gang of evil musical gypsies (can I put that nowadays?) led by ruthlessly evil Englishman (that always OK nowadays) have developed an evil sonic beam that will eventually be used to wipe Britain out and put it out of its misery. They experiment first by destroying thousands of people in two quaint English towns, the beam "instantaneously shrivelling their brains" - the carnage and the bodies seemed to have been cleared away by the authorities in less than a day. Sebastian Cabot as Fouracada the evil second in command who was marvellously over the top, is warned by Barton that "The Indemnity For Murder Is Not A Slight One" to no avail - I wish the film would have run another 3 hours just for their melodramatic battle of wills. The location shots of the stricken emptied town and later Blackpool and its Tower were very good and used efficiently. All I could remember of the film after last seeing it on TV in 1981 were the scenes in and up the Tower, I think that idea was a winner! During the climax the boss appeared to be using his suitcase in much the same way as a laptop would be - but he couldn't be - could he?
There are the usual silent stretches with background music for company as a reminder this was a cheaply made film, but Hammer did brilliantly well in disguising it.