a Hartswood Films production for BBC Wales in co-production with Masterpiece ; co-created by Mark Gatiss & Steven Moffat ; written by Mark Gatiss, Steven Moffat and Steve Thompson ; series producer Sue Vertue ; executive producers Beryl Vertue, Steven Moffat, Mark Gatiss, Bethan Jones ; directed by Jeremy Lovering, Colm McCarthy, Nick Hurran
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