Quickly... (The Zygon Inversion)

'Meanwhile, some people sang songs on the other side [ITV]. At a point where the BBC is seemingly under relentless attack, this is what a licence fee buys you. Karaoke is free, as long as you're happy to watch the John Lewis advert. Ambitious Saturday night drama has to be paid for.'
Den of Geek Review

Also, Phil Sandifer's review

ETA: I can't believe I didn't realise that this was broadcast the evening before Remembrance Sunday. That's some incredible planning.