I first heard about The Master of Ballantrae (1953) not as a movie or a novel, but as a play in a novel, World of Wonders, by Robertson Davies. An aging thespian in pre-War England would dig out this chestnut when touring the provinces. Even though he was far to old to play the swashbuckler, the audience loved that kind of melodrama. The movie is similar.
Based on a novel by Robert Louis Stevenson, it is the story of two Scottish brothers in the time of Bonny Prince Charlie. They decide that one will support the Hanover King, the other will fight with the Stuart Pretender. Then whichever side wins, their line will still hold Ballantrae. The older brother, the Master, is played by Errol Flynn. He is rash, arrogant, and rowdy, with a lovely noble fiancee and a woman in town. His younger brother, played by Anthony Steele, is the safer good boy. Of course, he will play the loyal role, while Flynn goes off to fight with the rebels.
He fights, and they lose at Culloden. He meets up with an Irishman, Roger Livesey and they flee to France. They get shanghaied and fall in with pirates, and generally have great adventures. In fact, the pirating is better than in a lot of pirate movies.
Flynn isn't really in shape for this kind of thing, due to the drink more than his age. But he gets away with it, partly because it's Errol Flynn and in his blood, partly because the material is just sure fire. Also, he's more than a bit of a rotter - I understand he's worse in the book - and it's a good look on him.
I can't say the same about the tartan trews he wears instead of a kilt. They may be historical (the Scots wore trousers with the plaid pattern on a diagonal as in the movie), but they just look silly.
In conclusion, a great swashbuckler.