As this episode heads towards what looks like another post-VOSDAL timeshift of 1.6/1.7m, I thought it might be helpful to post this from elsewhere:
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A 1.6/1.7m timeshift is about normal following an overnight within one or two points of 5m.
Look at the only two episodes to score overnights well under 5m. 'The Hungry Earth' and 'The Lodger'. Both got higher post-VOSDAL timeshifts than the episodes around them, to take them to the magic c. 6.5m point that seems to reflect the show's 'core' in a PVR/VoD world.
But then look at 'Vincent and the Doctor'. A 5m overnight, a fall of 0.7m from the previous week, but no compensatory post-VOSDAL timeshift (a slight fall in fact, though that's possibly noise around the roughness of the overnights).
In fact look at the five overnights between 5 and 5.2m (again, allowing for the overnights being rough), and you see no compensatory post-VOSDAL timeshifts, no matter how big the overnight fall from the previous episode (in each case a fall within one or two points of the one we saw for 'Hide').