UPDATE:

Thank you so much to everyone who's sponsored me/taken bets on whether I'd finish or not. I've been really (pleasantly!) surprised by the amount of people who have taken an interest, and even braved the hailstones to support me on the day.

I finished in a not-quite-record-breaking 4 hours 26 minutes, but did run the whole way...

Those of you with extremely good eyesight will notice I'm wearing a London Air Ambulance running shirt in the picture on the left, which HEMS were kind enough to give me (along with a tour of the Helipad and aircraft).

Thanks again for your sponsorship - it has gone to very worthy cause,

Gordon