Heaven Sent - Review

Naturally, all the press reviews are talking about Peter Capaldi's performance in Heaven Sent. Superlatives aplenty. So I don't need to go there. Take it as read that I agree with all of them.
For a 52 year old programme, that is now in its 9th season since coming back, there is no end to the possibilities offered by the format of Doctor Who.
I just gave up watching ITV's Dr Jeckyll and Mr Hyde, because it is degenerating into a "monster of the week" series. Primeval was just the same, Merlin sometimes so.
The problem these series always face is that they are stuck in the same setting, with a large central cast. There will be a story arc, but most weeks it is just the same old thing. Some monster or villain that is going to get beat round about the 40 minute mark.
"But surely that's exactly what Doctor Who delivers?", I hear the not-we cry.
True, there is a monster every week, and there is a story arc, but Doctor Who never ever feels like it is the same show week in, week out.
It can do really new things every single episode. It can go anywhere in Time and Space.
This current season has shown a definite desire to experiment with the format - sometimes in little ways, and sometimes like Heaven Sent.
So far in Series 9 we have had a lot more two-part stories, or single episodes that closely inter-link. We've had the Doctor address the audience directly, and even play the theme music (twice). Sleep No More skipped the opening titles altogether, and also gave us the found footage style of presenting an adventure. Face The Raven had a post-end credits scene that wasn't a "Next Time" piece, as well as seeing the companion departure before the series finale (maybe). That last point is not new to the series as a whole, but unusual for Nu-Who.
This time, we have 50-odd minutes of just the Doctor on his own. There's a memory of Clara in his head to talk to, and bounce ideas off. He can talk to the monster - the Veil. He can also challenge whoever it is that has sent him to this weird clockwork castle, whom he presumes is watching and listening. The only real person he talks to in the whole 55 minutes is a little boy on his homeworld of Gallifrey in the closing moments.
Yes, Gallifrey. I predicted Time Lords last week (easy if you looked for the clues). I was a bit upset that the new Radio Times was published on Saturday morning - with a big picture of Donald Sumpter as the Time Lord President - before Heaven Sent aired.
Thanks to these BBC authored spoilers, the big reveal at the end was, well, spoiled a little for me.
I did not expect the Doctor to reveal that he is the Hybrid that has been mentioned throughout the series. (Is this going to address the half-human controversy from The Movie? Humans would be the universe's most ruthless warriors if it ain't the Daleks).
Nor did I guess what the heck was going on with that castle. The idea that the Doctor had been there thousands of times before we first saw him - so all those skulls were his - was a shocker.
I suppose Heaven Sent now bags the record for the story with the longest time span by billions of years.
No doubt you will have already seen the photos for next week's episode, which runs to 65 minutes? No? Well Blogtor Who has them. Avoid if you hate spoilers. (I looked but thought that they would have been published by everyone else). There is also the trailer, which looks far cooler than the "Next Time" tease.