London Conspiracy (1974)

Life is never dull where Lord Brett Sinclair and Danny Wilde are concerned. But who would expect dire danger, hilarious though it may be, to face them in one of Brett's baronial homes? Even more unexpectedly, murder and black magic take place when Danny decides to own his own little piece of England and buys a tumble down old cottage. The old mansion, Greensleeves, has been in the Sinclair family for generations, but has been unoccupied for a long time except for an aged butler named Moorehead. It is only by chance that Brett discovers that it has been restored without his permission. He and Danny decide to investigate and, entering through a secret tunnel, find a letter addressed to a theatrical agent asking him to an actor who resembles Brett. Brett promptly poses as the actor and gets the job of impersonating himself. Danny and Brett have a lot to overcome before Danny can enjoy his little piece of England!