The Case of the Undiscovered Corpse by Charlie Cochrane

Alasdair Hamilton and Toby Bowe are the darlings of post-war British cinema, playing Holmes and Watson onscreen and off. When they’re called on to portray their fellow amateur detectives—Orlando Coppersmith and Jonty Stewart—not only do they find distinct challenges in depicting real people, they also become embroiled in solving a century-old murder.
How did a body lie undiscovered so long in the Stewart family vaults, who’s been covering up the murder ever since and why was the victim killed in the first place?