The Doctor's Meditation

In the UK. the BBC have released The Doctor's Meditation - the prequel to The Magician's Apprentice - on the official Doctor Who Facebook page.
Running just over 6 minutes, it shows the Doctor staying in a medieval castle - not unlike the one we saw in the Robin Hood story last year.
He is planning on meditating before he goes off to see a very old acquaintance. Someone who he abandoned, which he regrets.
He's found himself a squire named Bors, whose life he saved. (He removed a splinter...).
The Doctor finds a number of ways of putting off his meditation - and hence his departure. He has the locals spend weeks digging a well, for instance.
He's very bad at conjuring tricks - though he does like to do Tommy Cooper impressions when he practices them. The Doctor also likes to duel with Bors using his spoon.
The piece ends with the Doctor finally settling down to meditate - but first he tells Bors about the many battlefields he has seen - and we get a glimpse of the one that we know is going to open tomorrow evening's episode.

Capaldi is as funny and as rude as last year. Bors would make a brilliant companion in my view.
Who might this person be that the Doctor has let down? There's an obvious one, but Moffat does have a habit of creating very old friends that we have never heard of before.
Apparently the BBC are going to release Series 9 in two parts on DVD (and presumably Blu-Ray as well) with exclusive extras.
The other big news today is the confirmation that Jenna Coleman will, as expected, be leaving at the end of the series. Room for Bors, then...