I bought a ticket for the £100m lottery last week. Not out of desperation. The construction of Tree House has cost more than anyone anticipated, but we can still afford to live there without selling our souls. What's the point of a good credit rating if you don't make use of it, I say.
I bought the ticket simply to participate in the national contemplation of limitless opportunity. Perversely, in this existential moment I found myself recoiling from the thought of spending any money at all. To a degree this is because we have been shedding so much cash over the past 16 months that I am keen to stop for a while and enjoy the rewards of all our spending. But more profoundly, I realise that my ambitions post-build are remarkably frugal.
Tree House has been a big investment of money, resources and energy, but when we're living there (in three weeks' time) we will be self-sufficient in energy and very thrifty in our use of water and other resources.
Without doubt it will also be a delightful place to live. Our newly completed kitchen, a work of bespoke joinery by local cabinet-maker Stephen Edwards ( www.ecointeriors-uk.com), expresses our ambitions for the house very concisely.
It includes low-impact materials, appliances that consume a minimum of energy and water, low-energy lights and lots of built-in recycling capacity.
But above all it's dead gorgeous, designed to make cooking a joy. If there is such a thing as "contemporary frugality", perhaps this is it: a wonderful, low-impact space that we won't want to leave, however many high-energy restaurants beckon from Clapham High Street.
My lottery ticket has made me aware of how fully I want to explore this conjunction of delight and eco-frugality in all aspects of my life. For example, since I stopped shopping in supermarkets I have become a regular visitor to Pimlico Road farmers' market and have discovered the specialities of local shops that I previously ignored. Shopping may take longer, and sometimes cost a bit more, but my food miles are radically reduced, the local economy benefits, the produce tastes better and the experience is a genuine pleasure.
Another key decision has been to get rid of our car once we have moved in. Having recently started cycling again in preparation for this moment, I have been struck by the pleasures of cycling in London's back roads, especially on bright winter days when the richness of the capital's architecture surprises you on every street.
More radically, I have decided never to fly again. This choice may narrow the geographical range of my travel options but are there really any earthly pleasures that cannot be enjoyed within the bounds of Britain and Europe? And shouldn't travelling itself be a pleasure rather than an infernal ride in a dehydrated sardine tin? (If Chris and Jess in Sydney are reading this, don't worry - we'll get there eventually, albeit via a much more interesting route than most people ever contemplate.)
I have always insisted that there are no hair shirts in my wardrobe and that Tree House will give us everything we want from a home. Given these wider decisions, you may suspect that I have been wearing hessian underpants all along. Perhaps you are right. Or perhaps I have been awakened to a basic reason why people have always chosen to live more simply: life's just more interesting that way.
So what will I do with the £100m, given that I won't be rushing out to buy fast cars and a private jet? Easy: I plan to buy everyone in London a packet of courgette seeds, a guide to the National Cycle Network and a day return to the seaside.
Risky though: if all 7 million of us have a glut of marrows next August, there'll be hell to pay.
'The Complete Diary of an Eco-Builder' will be published by Green Books in May. www.treehouseclapham.org.ukReuse content