Well -- I'm just home (before midnight!).
Summary (I may add more detail tomorrow).
токамак beasted me properly (without breaking into a sweat).
I actually bonked fully (mid-afternoon carrot cake wasn't enough) and got shakes, tunnel vision etc. about a mile form the end, and limped to the pub, where I consumed orange juice and lemonade (for the sugar) and crisps and nuts to try and stave off the shakes etc. (Oh and an Oscar Wilde and a few Drops of Nelson's Blood to follow)
chief was already there when токамак dragged my sorry arse to the pub. bobb arrived soon after and wowbagger wasn't too far behind.
I also got the shivers rater badly, and despite donning my arm-warmers and gilet, was still suffering. chief lent me a jacket to put on top to try and stave them off. by about 11pm I was feeling relatively human again, and set off towards chelmsford station, shepherded for the initial part of the journey by chief (who'd also lent me a hat and full-finger gloves by this time). In fact, once we parted company, and I'd stopped at the petrol station en-route to the station, for a bag of wine gums, I felt much better and seriously considered ridin home anyway, until common sense got the better of me.
I seriously got my fuelling wrong on this occasion.