The first series contains six episodes. It premiered on BBC One on 6 January 2018, with all six episodes subsequently available on the same day via BBC iPlayer. The series premiered on Hulu in the United States on 7 March 2018. The series has also been acquired by the Seven Network in Australia , ZDF in Germany and SVT in Sweden . The first series was released on DVD and Blu-ray on 19 February 2018.