So, how did I get on with my attempt to escape the tyranny of the clock?
Well, in the end, my need for routine won out over my desire to rebel against chronological authority, and I didn't notice any particular benefits to allowing myself to be ruled by nature.
Partly this is because I've started really wanting to go for a run in the morning, and I like this to be early, before too many people are about - and also to allow time for a decent outing and to be back in time to do all the other stuff I need to before work. I want to be able to do this at least semi-regularly to get into a sort of routine, and relying on whether I woke up at the right time by chance isn't going to work - I was waking any time between 4:30 and 8:00 - but somehow the later mornings seemed to be working days. Naturally or not, I do like to be up bright and early, and I'm at my best then. I didn't notice I was feeling any better for not waking up with a regular alarm, and wasn't settling into any predictable pattern naturally.
It's really, really hard to avoid knowing what the time is, and thus subconsciously - or consciously - being influenced by it throughout the day and evening. And the more you try to avoid it, the more aware of it you become.
I have found, though, that I tend to spend less time lying awake worrying about the time without the radio alarm clock's display beaming out at me, so I won't be fetching that back down from the attic. I've been using the iPhone, but rather than just using the alarm, I've sussed out the 'bedtime' function. It's easier to see and change the time and days the alarm's set for, and it has much nicer sounds (I'm favouring 'Helios', which is a lovely gentle introduction to the day). I'm trying to resist the temptation to look at it still if I wake in the night.
So I'm back to regularly waking up at six - and actually getting up then now, rather than lying listening to the radio for twenty minutes - or five thirty if I'm having a run, and I think that regularity suits me better. The early morning is definitely my most productive time, and if it's one of those days when I do need to be in the office for a 9:30 meeting, I can be there at 7:30 and get more done in the hour and a half before everyone else arrives than the rest of the day put together. On the days I didn't get out of bed until eight, that felt very much a wasted opportunity - and I didn't feel any perkier for it.
So - with a few tweaks - it's back to the old routine. Which, I think, is definitely better than no routine.