produced in association with the Canadian Broadcasting Corporation ; executive producers, Sally Bochner, Kent Martin ; directed and written by Barbara Doran
created by Mark Gatiss, Steven Moffat ; produced by Sue Vertue ; executive producer Masterpiece, Rebecca Eaton ; executive producer for BBC, Bethan Jones ; executive producers, Mark Gatiss, Steven Moffat, Beryl Vertue ; Hartswood Films production for BBC, Cymru Wales in co-production with Masterpiece