I am a guinea pig

I'm not allowed to give blood (some teenage jaundice), and I doubt there'll be many takers for my clapped out old organs by the time this cadaver is ready for disposal, so the invitation to contribute medical research data to the UK Biobank came as a rare chance to demonstrate a little altruism.

In one of those depressingly anonymous office blocks in Croydon, I joined a fair number of other people passing through a (very efficient) conveyor belt of assessments and tests.

Signing away all rights to my urine (the commercial possibilities of which escape me for the moment) and blood samples (no more than three teaspoons, they assure you, which neatly stops anyone making jokes about "very nearly an armful"), racking my brains trying to remember, amongst other distant history, just how many childhood episodes of sunburn I suffered (a lot, I think, but is that just the memory of the stories we tell ourselves?) and happily punching the screen through the computerised hearing and mental recall puzzles, I passed along the chain of technicians and their various physical assessments.

There were the familiar weight, lung volume (the lady in the next cubicle was having an operatic time of that), exercise and bodily fluid tests (blood comes next to last, no doubt in case of fainting fits, and the - ahem - other samples discreetly round the corner).

I see medical people so rarely, there is always some amazing new equipment, and for an operation like this, even more so: scary machines to photo my retinas, pocket-sized computers linked to a plastic clothes-peg on my thumb that between them graph out my blood circulation. And the output from everything is automatically stored on a simple pen-drive to carry on to the next technician.

After a last bout of confessing shaming truths to the computer about diet and physical activity (How many minutes a day do I actually walk anywhere, and does shuffling to and from the kettle count? What exactly was in that sandwich I ate yesterday?), I collected the only visible token of my contribution to science, a printout of the immediately available vital signs (no, not even tea and biscuits). Hardly surprising to be told I can afford to lose a bit of weight and need to watch my blood pressure, but reassuring that my heart and lungs are sound. I'll probably be bulking out their averages column for a few more years yet.