Many people spotted the production crew out in force in Cardiff city centre yesterday. Here are three shots from Freema Agyeman's fan site where she is seen with co-stars David Tennant and John Barrowman both filming scenes and comparing puffa jackets.
I've kept back the more spoileriffic ones - more can be accessed by this Digital Spy post.
Meanwhile David Tennant and his "Runaway Bride" co-star Sarah Parish can be seen on BBC One on Sunday night in Tony Marchant's "Recovery". David is likely to pop up on TV and radio to promote this in the next couple of days.