Did you spot the sneaky River Song callback in this week’s Doctor Who?

“Oh go on try this at least, it’s my favourite,” The Doctor tells Bill as he struggles with the local delicacies.

“Your favourite?” Bill asks incredulously. “What, you’ve been here before?”

“Oh yeah – a few times,” the Doctor replies.

And as some fans with particularly good memories may recall, one such visit has actually been chronicled in the series before, with the Doctor taking wife River Song there offscreen prior to the events of 2011 episode A Good Man Goes to War.

“It’s my birthday – the Doctor took me ice-skating on the River Thames in 1814,” River tells Rory (Arthur Darvill) in the episode, confirming that she and the Doctor had actually visited the very same event that he’d later take Bill along to (while wearing period-appropriate clothing, above).

“The last of the great frost fairs. He got Stevie Wonder to sing for me under London Bridge.”

Now, of course this doesn’t mean we’d see the Doctor and River scurrying around in the background of this week’s episode to the strains of Isn’t She Lovely – the fair lasted four days historically, so they could have been there at a different time to this new trip, which only took place on the final day – but it must have been a risk, and it does raise questions about why this series has made quite so many references to River Song this year.

Just think about it – the Christmas special had a decent chunk of story devoted to the Doctor’s grief over her death, the first episode of the series saw him keeping a picture on his desk, and even last week saw the Time Lord reminisce about a mutual fish friend they shared.

If we didn’t know better, we’d say series showrunner Steven Moffat is priming us for one final return for the character he introduced to the series, before he and Capaldi leave this Christmas. Watch this (time and) space.

Doctor Who continues on Saturdays on BBC1 at 7:20pm