[IanJRedman]

Previous Whittaker stories have been (maybe?) upscaled to UHD but am I right in thinking these are the first shows shot in UHD?

There are two Whittaker episodes available on iPlayer in UHD: Revolution of the Daleks, and The Power of the Doctor. Whether those were shot in UHD or upscaled, I can't say for sure, but I was under the impression the BBC don't "do" upscaled UHD?

For these new episodes though, there is absolutely no question that they're shot in native UHD: you can see it on the filming monitors in the backstage stuff.

It's a bugbear for me though, that they aren't releasing the UHD versions of these specials until immediately after the episode has screened on BBC One in HD. I assume it's because if they wanted to make the episode available in UHD "live", they'd have to release the entire episode upfront on iPlayer, which would make it possible for people to jump ahead of the live broadcast... But it's unnecessarily compromising the experience for UHD viewers, as it means you have to choose between watching live in HD SDR, or waiting for the UHD HDR version and watching behind everyone else...