Over the weekend, I caught up on some sleep. I’ve said before, my “core sleep” hours are between 7 and 9 am – if I get woken up (or have to wake up) within that time, I’m foul for the day, and resemble a grizzly bear woken from hibernation.

Come the end of those core hours, I usually wake up naturally within a couple of minutes, and all is right with the world. It’s weird, but true.

Anyway, this weekend I couldn’t work out why I was waking up at 10am instead.

And then it occurred to me.

It looks like my core hours are actually 7 to 9am GMT. We’re in BST, so that’s 8-10am.

Bizarre, but true.