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
a co-production of Mammoth Screen and Masterpiece in association with ITV Studios ; written and devised by Russell Lewis ; produced by Tom Mullens ; directed by Sandra Goldbacher, Bryn Higgins, Lawrence Gough, Olly Blackburn