This is a very strong opener, with Alex and Cass and their conflict as a focus point after the end of the last set.

The Downton abbey setting is pretty cool and the mystery surrounding the auction and the identity of the employers of the mansion gripping. The Codicil, the Sontaran-Timelords, Alex's choice with the TARDIS key and the twist at the end with the Doctor are all really good and engaging.

It meanders a bit though and doesn't feel as neatly plotted as other stories but as a first part works wonderfully and I expect the quality to keep rising.