Lot of rubbish written in this thread today.
"How dare the BBC aggressively schedule against Broadchurch? Evil b**tards! They should have shown a repeat of a BBC4 documentary about coffee plantations. Disband them immediately! Moan, moan, moan."
Broadchurch was supposed to be the biggest show on television this year. It should be able to cope with a bit of competition from a programme that's not only 18 years old, but one of the least fashionable dramas on TV. It doesn't have any critics ranting and raving about it and, as far as I can make out, it doesn't even get
nominated for awards, never mind win any. Whereas Broadchurch won loads of awards including 3 Baftas.
In addition Broadchurch inherited an 8.7m audience from Coronation Street whilst Silent Witness followed on from Panorama which had 3.5m.
I also don't get why we're not supposed to have drama against drama. We've
always had drama on against drama. Back in the days of the Nine O'clock News, BBC1 had two post-news weeknight drama slots, Tuesdays and Fridays, and they were always on against drama on ITV. Plus on Sundays we would get Howard's Way against The Ruth Rendall Mysteries or London's Burning against Pride And Prejudice. And, of course, last Autumn we had Cilla and Grantchester on against New Tricks and it was New Tricks that took the hit so what are you going to do about it?
Dancc said he didn't think the BBC would be thrilled by how SW is performing in the overnights. I disagree. 5.87m would be a solid overnight for SW against ITV low-rated Tuesday factual. Against "the biggest programme on TV this year" it's brilliant.
That overnight is compatible with the standard overnights of such critical smashes as Happy Valley, The Missing and Last Tango In Halifax (before Last Tango got a leg up from Call The Midwife). It puts it above New Tricks which collapsed big time last Autumn, it puts it above Lewis which performed underwhelming last Autumn and it puts it above Foyle's War, which has collapsed badly this series. (This may be Last Series Syndrome. Maybe we will see Silent Witness collapse when the BBC announce its last series, although I'm not sure if many of us will live long enough to see that.

)
In addition, Silent Witness timeshifts just as well as any of these other dramas. The recent Wednesday episode timeshifted over 2m, so last night's episode should be very close to, if not above, 8m. That's pretty good going for an 18 year old drama on against "the biggest programme on TV this year".
Poor old Broadchurch is suffering that "difficult second album". As others have said, in so many words, the success of the first series created a rod for its own back. Some people think it's still brilliant but others have been disappointed and that has resulted in the fallen overnights. And we've yet to see how much episode 2 timeshifted.
But none of this alters the fact that Silent Witness was able to cash in on Broadchurch's slip. Doubt very much if The Musketeers or Traffic Cops would have cashed in so much.