From his website:
TRAINING OUTLINE
Over 5km and 10km it may appear that I do not have the pace to run a 2 hours 30 minutes marathon
No kidding, his best 5k is 17.09, that's outside 72mins pace for a half.
A 2:15 marathon is pretty much bang on 16 mins for each 5k, he should try running one of those before planning to do a marathon at that pace.