MPG Marathon - Diesel Road test

And we haven't even started driving yet. John produces complex graph showing power, against torque and speed. It's disturbing proof of closet egg-headedness, but by golly it's useful, showing that we must keep that rev needle just below the 2,000rpm mark. We can't let it wilt too low, but rpm, dear driver, not mph, is the key to spendthrift transport. In tarmac terms, our quest for the tingling pleasure of the instant 999.9mpg readout is achieved via lowest possible revs in highest possible gear at lowest possible speed. And it spells a sequence of bizarre other-worldly motoring moments: being overtaken by a succession of irate caravanners (try it, it's fun); amassing a tailback of what seem to be enough fans (well, they were waving their hands a lot) to move a JCB driver to tears; and most relaxing of all, cruising effortlessly down the motorway - at a serene 42mph.

The rules of the AA/ALD Automotive MPG Marathon are understandably strict: you can't at any point turn your engine off while in motion (and remote telematic monitoring from sponsors Quartix would ensure they'd know if you did); you can't push the car along the monitored route, interfere with the seals on the fuel cap, or jettison dead weight, such as bad navigators. But you can coast, slipstream lorries (within safety margins, of course), avoid braking at all possible moments and restrict your breathing to avoid window misting (see above). And you musn't speed, though the results showed someone managed 87mph. It's possible woke up, remembered they had a life and panicked.

Some of this is, frankly, counter-intuitive anorakery. But with 86mpg in bold at the end of our first day's leg in the car park of the Headland Hotel in Newquay, it's an anorak we wore with pride. Surely only freaks could beat us now, we whisper like kids.

Freaks didn't. But by the end of the second day, a succession of infernal setbacks - suicidal tractor drivers, loose freisians, Bristolian traffic glue and, worst of all, a trigger-happy fuel attendant who overfilled our tank on the final brim test, thus dashing a whole teacup of our savings onto the forecourt, conspired to confine us to a respectable class win, our 83.98mpg consumption just inches from ultimate glory.

Ah well. Citroen now knows its C2 van can tackle all sorts of motoring misery and emerge with unbeatable cred in true-life testing. And okay, some blokes in a Toyota Aygo managed 84.4mpg, but they were considerably thinner than me and John, had a smaller car and slipstreamed us there and back.

"Your father's so mean," my mother once told me, "that if he found a plaster he'd cut himself." Obviously I've let my lineage and Tiscali down today, but just you wait till next year. I'll show you mean.