Line Of Duty hit a new record for the TV drama, with 9.6 million viewers.
The police corruption show returned to TV on Sunday with stars Vicky McClure, Adrian Dunbar, and Martin Compston reprising their roles, and Kelly Macdonald joining the cast.
It averaged 9.6 million viewers, a peak of 9.8 million and a 44.4% share, making it the biggest overnight rating for a Line Of Duty episode, the BBC said.
It beat the finale of the last series, which had an overnight figure of 9.07 million.
The figures also make Line Of Duty the biggest drama launch since 2014, the BBC said, when Call The Midwife was watched by 9.6 million.
The new series sees anti-corruption unit AC-12 take on a new case, but DI Kate Fleming (McClure) is no longer on the squad, and is working on a murder investigation with a different department, which has come under suspicion from AC-12.
It comes after the show’s creator Jed Mercurio said killing off the three stars of the show is “never far from my thoughts”.
“We all get on brilliantly, but everybody knows that we’re serving something bigger than ourselves, which is Line Of Duty, and one of the things about the show is that nobody’s safe; it’s what keeps the audience on the edge of their seat,” he said.