Lots of people who DNF will drop out on the highway, so seeing someone step off the road wouldn't be unusual. Easy enough to get to Westminster on the tube from there, and then slip back into the race rather than go round to baggage collection. Somewhere along birdcage walk would be the obvious point, the marshalls are at the crossing points so inbetween those you'd get back in with no problem.
Bainspj - I had a club place years ago, and I gave an estimated time when the entry went in and got a pen allocation based on that. Just like a ballot entry, in effect. Blue start. Put 3 hours on your entry and you'll be in pen 1 behind the champs runners.
Nobody has suggested that cheating in a race is a criminal offence, but I'd be happy to take the piss out of someone on a running forum who is known to have cheated in a race and is then rude to someone trying to find out a bit more.
Especially when they post photos of themselves on facebook with their medal. That rules out the "it was all a mistake I was just getting to the finish to get my bag" excuse that's been used in the past.
Re boosts: I can't discern much difference between the adios boost and mizuno ronin, apart from the ronins being a touch lighter and unfortunately discontinued. The boosts are more pricey but that's offset to an extent by being more hard-wearing.
I was pretty done in at the end last Sunday but a light week has sorted that out. My plans to run at Richmond next weekend have been scuppered by family arrangements so the next race may be the BUPA 10k. I suspect I won't be the only thread representative at that one.