Not being familiar with the Clegg/Syn/Scarecrow story, I saw Cushing as the sort of benign character who turns out to be a vicious criminal in stories like these. And for a while I was uncertain of who would be the heroes and villains of the movie. That frightening to death of the old man made the smugglers (presuming them to be the night riders) to be rough customers and dirty dealers. But the naval detachment that comes to town looking for contraband is shown as a bunch of boors and bullies, and viewers more familiar with the Thorndike stories or English history might more readily recognize them as agents of an oppressive government. Blyss/Clegg himself is a stern leader but insists on no violence against the sailors, and is later shown to be a genuinely benevolent man in his new life, concerned for the well being of poor villagers and his own daughter, who believes herself adopted by Blyss. These are mixed signals for whether to root for him or not, but the authorities are clearly no heroes, if not villains either. The nearest thing to an unambiguous hero is Harry Cobtree (Reed), the local squire's "freethinker" son, a rival for the hand of Blyss's daughter, and more besides. It's he and his love who'll have a happy ending here, if anyone does.
Milton Reid, as "The Mulatto," the unlikely pirate who scored with Mrs. Clegg and suffered for it. He survived to be found by and become the pet and bloodhound of the naval captain who investigates the smugglers.
The subject matter may make Captain Clegg too obscure or just not scary enough to be part of the essential Hammer canon for many American viewers, but I enjoyed seeing more proof of the great studio's genre diversity. The repeated reminders via DVD in recent years that Hammer did much more than horror have been great news for movie fans, and the good news in this case is that Captain Clegg is eighty minutes of easygoing fun.
Hammer downplays the scarecrow angle in its version of the Romney Marsh story, perhaps because Disney would play it up, but the straw man does put in a few dramatic appearances.
Universal really plays up the terror elements for all they're worth, and more, in this trailer uploaded to YouTube by justjoined.