A long clip from The Clocks by Agatha Christie is here (but cannot be embedded in this post). It includes scenes inside and outside some of the houses where it was filmed in 2009.
This is said to have been the last performance of Anna Massey before she died.
The entire series of films with David Suchet is expected to be completed this year.
The tree house in Barnsbury Wood was built without being attached to the trees.
The still shots below are from the ITV screening.
The short clip below is just a trailer.