This is an HD recording. It was recorded from BBC1 HD channel. For some reason, it is not tagged as HD.
Could it be something to do with the way I have my channels arranged, with the SD version of BBC1 for example, mapped to the HD channel?
Yes. The tags are copied over from the guide data, not the recording itself. So if the guide data for the recorded program includes the HD tag, then it will appear in the recording. However, if the tag was not present in the guide for the recording, then it will not appear in the recording either.
Also, as I understand it, Gracenote's guide data outside the US leaves a bit to be desired.
The thing is, the guide for the HD channel will have included an HD tag and it would have been set to record from the HD channel. But I think there might be a bug here that when set up as I have it, it pulls the guide data from the non-HD channel.
I think for now, I’ll take another approach to forcing HD instead of SD and just disable the SD channels.