Where once it was Lady Sybil escaping the confines of Downton to indulge in a bit of Suffragist role play, now it’s Lady Rose seeking to slum it with the under-classes. Where once O’Brien allied herself with Thomas against the saintly Anna and Mr Bates, now it’s Edna Braithwaite.

Perhaps this is a sly comment on how resistant country houses are to great change – or perhaps Downton is just a programme that knows a good formula when it sees one.

The trouble is: like so many programmes that, where casting is concerned, seek to replace like for like, the replacements aren’t quite as engaging as the originals. Footman Alfred is as stolid a character as William once was, and has the same tendency to moon over the servant girls, but he’s harder to care about. Meanwhile, until tonight’s episode at least, flapper Rose had much of Sybil’s flightiness but little of her moral conviction.

No one wants a Marie Antoinette who plays milkmaid – even one who eyes up the under-gardener for his ‘good craic’. So it was encouraging, at least, to see Rose extricate herself from the attentions of Sam Thawley with something approaching good judgement and even a little tenderness. If she can just curb her tendency to regard the working classes as theatrical playmates, it’s possible she may prove a worthy successor to Lady Sybil after all.

There was no way Rose’s infatuation with Sam was going to run the course. The woman may have a fondness for a man who can use his hands, but she’s all imagination and no experience – unlike Mr Bates, whose comment to Anna tonight, ‘Don’t I keep telling you? Prison was an education,’ set all sorts of alarm bells ringing. In exactly what context has Bates been sharing his prison education? And did it make his ever-changeable limp better or worse?

It’s enough to make you applaud at the archness of it all. But Rose’s adventures tonight were not the only ones that had a flavour of the theatrical, as Carson’s music hall background came to haunt him with the grafting on of a story about lost love.

Given that this is Carson we are talking about – a man whose stoic decency could make a nation sniffle into its Horlicks – this storyline should have been more of a lip trembler. But Downton is so often all tease and no climax when it comes to following through its storylines, and, before the first commercial break, Mrs Hughes had sussed that Carson and his former partner were being a right pair of Charlies, both literally and metaphorically.

That’s Mrs Hughes all over: sharp-eyed, commonsensical and prone to pass among the upper and servant classes like gonorrhoea. She’s like a walking homily that woman, and when she’s on the case, even long-standing disputes in love can be resolved with merely a censorious or wistful look.

By the end of the episode, Charlie Grigg had been whisked out of the story to Belfast of all places, where presumably he’s in no danger at all from contrived historical vignettes.

Next week: Nigel Harman and Kiri Te Kanawa. We can’t wait.

Aired at 9pm on Sunday 29 September 2013 on ITV.

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