You can do this by identifying a few people who fit the bill - based on last year's published results - and make a list of them. You then check this year's entry list and if they're there, memorise their numbers. On the day, you mill about at the start, find them, and stalk them.
Creepy but usually effective.
The main problem is that they might be top runners who were injured last year and just jogged round, in which case you'll be wearing your eyeballs as jewellery by PYG summit.![]()