So, RY's bib number at London 2015 is 2476.
these are his splits (prob won't copy/paste well):
Split Time Of Day Time Diff min/km km/h Place
5K 10:27:37 00:17:31 17:31 03:31 17.13 -
10K 10:46:37 00:36:31 19:00 03:48 15.79 -
15K 11:06:25 00:56:20 19:49 03:58 15.14 -
20K 11:27:54 01:17:48 21:28 04:18 13.97 -
HALF 11:32:24 01:22:18 04:30 04:06 14.65 -
25K 11:49:25 01:39:20 17:02 04:22 13.75 -
30K 12:12:34 02:02:28 23:08 04:38 12.97 -
35K 12:36:28 02:26:22 23:54 04:47 12.55 -
40K 13:08:20 02:58:14 31:52 06:23 9.41 -
FINISH 13:17:45 03:07:40 09:26 04:18 13.98
From these splits it doesn't look like he stopped to talk to anyone on-route.
I know the course and I've checked out his photos (link from his results page) and there is a photo of him passing Cutty Sark (boat) behind him are runners number 797 and 900 (both of whom finished in sub 2.40 with reasonable pacing and ran faster HM splits than him. Cutty Sark is around 6.5 miles into the race so it seems to me that he did run it all - he just went off like an idiot - first 5km downhill remember - and then slowed all the way after that. His 1.22 HM means that yes, he could be a decent runner if he trained properly.
So bearing in mind that he looked fit in the RA USA around that time, he was somehow training himself whilst on that multi day run in the US. So, I for one don't believe he was putting in all the miles on that event. Maybe run hard for 2 miles (good bit of tempo training every day) someone picks him up in a car & drops him further down course (same person who gets him to and from the US airports for his trip to London marathon) - he jogs home for 10-15 miles (good endurance training) = gets fit for London marathon.