This was 1.5M viewers down on the 7.2M who tuned into the series premiere last week, making it the biggest new drama launch on British TV in more than five years.
It is not uncommon for TV dramas to lose viewers for their second episode, and a fairer reflection of the audience will come once catch-up and online viewing through iPlayer is factored in for the Philip Pullman adaptation.
Despite the drop off in audience, His Dark Materials comfortably beat competition on other channels on Sunday night and peaked with 6.2M viewers.
The episode will air on HBO tonight, and features the young protagonist Lyra Belacqua being taken in by Mrs Coulter as she remains desperate to find her friend Roger Parslow. The first installment was seen by 700,000 viewers in the U.S. last week, making it one of the best debuts HBO has seen on a Monday.
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