Every time I read an article like this, the waking time gets pushed back by an hour each time! Who now is going to write an article recommending that you should wake up at 3am (which is right in the middle of my REM sleep period)? I’m still getting to grips with waking at 6.50 am in the middle of Winter thank you very much.

Waking up at 4am is NOT sustainable for most humans - maybe if you’re a vampire! :-)