T he admirable actor David Haig has a sprightly sideline as a writer of historical bio-dramas. My Boy Jack (1997), about Rudyard Kipling’s mourning for a son killed in the first world war, and Pressure (2014), concerning the Scottish meteorologist charged with finding Gen Eisenhower’s weather window for D-day, is followed by Magic, dramatising the fraught friendship of two giants of entertainment between the wars: Sir Arthur Conan Doyle and Harry Houdini. It overlaps with My Boy Jack in that, like the author of The Jungle Book, the creator of Sherlock Holmes is grieving for a war victim son. The hope of a reunion brings the writer to the spiritualist movement but creates tension with Houdini, the illusionist convinced that seances are as much a theatrical pretence as his own escapes from straitjackets and water tanks. Happy to have the Scot as a fan, the Hungarian-American is alarmed to discover that the writer believes him to be blessed with supernatural powers.…