His 3:07 in London is valid. He has every 5km split, start and finish time. The course is fully lined by spectators, so there's nowhere he could have left/rejoined without being visible, and he was in his very recognisable kilt. He can be seen running from the start line in the BBC TV coverage. He can be seen at all the photo points along the route alongside other runners with his splits. There's video of him trying to keep up with the Paula train during the first 5km, and more video of him stopped talking to his support crew around 24 miles.
The 3:07 is valid and I wouldn't bet against a sub-3 with the same training but without such stupid pacing and that ridiculous kilt.
I agree. People have cheated at London but then they have 5km splits missing. See for example: http://www.independent.co.uk/news/faux-farah-jason-scotland-williams-faces-probe-by-london-marathon-bosses-over-claims-he-cheated-his-9271231.html.
For Rob to have all his splits and be photographed at numerous locations and still to have cheated, he would have to have a teleportation device.
Plus, he claims his marathon PB is 2:41, Why go to the trouble of cheating his way to a 3:07?