I set off at seven in the morning and ran without stopping until half past nine. It was by far - by a whole hour, in fact - the longest period of time I've failed to walk, sit or lie down in my entire life. When I arrived back at the cafe at Springfield Marina I was ready to drink their cold taps dry. You might have already guessed that I'm training to run in next year's London Marathon (and, indeed, for another marathon before that). I recommend anyone else seized by a similar combination of valiance and foolishness to do what I did last Sunday and run all the way from Millifields swings to Enfield Lock and then (most of the way) back again.
The insufferable self-satisfaction of completing the time specified in my training programme was just one of the pleasures of the run. The tranquility of that dewy early hour, with the sun breaking through, was just about unbeatable. Then there's the enhanced awareness of space and distance you somehow enjoy from travelling by foot: from Springfield you mark your progress lock by lock, first Tottenham then Stonebridge, Pickett's, Ponders End and finally Enfield, where you're less than two miles from Waltham Abbey, which is outside of London altogether. I might even have made it to Hertfordshire.
Then there's the interesting people you meet. Who were those young men and women meandering through Millfields with the mannered smugness of those who've been doing something they think a bit subversive? What sort of life is led by that solitary fisherman sat under a bridge in Edmonton amid twisted wire and litter in the least picturesque section of the riverbank? Was the man navigating that narrowboat who waved and called out a cheery "good morning" real or a figment of my imagination from some childhood picture book?
Some time this weekend I plan to do the whole thing again only for half an hour longer. That ought to bring me the whole way back to Millfields swings, rather than halting at the 150 minute mark at Stonebridge on my return journey and walking the last bit. If I succeed I promise not to boast - at my delicate speed I will, after all, need to keep going for quite a bit longer if I'm to complete a marathon.
As well as dragging myself along the Lee I've begun running my way across the whole of Greater London in installments, from west to east, Uxbridge to Upminster. The plan is to pass through all 32 boroughs and the City along the way. I'm documenting each leg of that endeavour on my Guardian blog - see here, here and here - and inviting readers to sponsor me. I'm raising money for Shelter, which complements my journalistic interest in London's deepening housing crisis. If you would like to contribute, please click here. All contributions, no matter how small, will I'm sure be greatly appreciated by that distinguished and excellent housing charity.