Written by showrunner Steven Moffat, the two-parter is co-produced with BBC America and saw Smith and Gillan joined by Arthur Darvill and Alex Kingston to film scenes in the Utah desert last November.

Moffat commented last year: “The Doctor has visited every weird and wonderful planet you can imagine, so he was bound get round to America eventually! And of course every Doctor Who fan will be jumping up and down and saying he’s been in America before. But not for real, not on location – and not with a story like this one! Oh, you wait!”