14 locks is actually 20 anyway, if you count the 6 before you go under the M4! It's a nice run that, pretty challenging for me especially the initial staircase of 5. I normally head up there at least once a week (Crumlin arm) as far as Cwm Lane then come back along "top road" (I live near the Civic Centre).
You're right about the kids - in Cwmbran they probably don't bother hiding lol.
It's supposed to be ultra-flat, on the Caldicot Levels innit? I'll be there, I just hope there isn't too much wind (memories of my last 10k at Dorney Lake - all 4 seasons in one race and a b*gger of a wind blowing).
To be fair I am getting variable results. I think I'd be happy with accuracy for a normal "steady to hard" training run, but my 70% MHR run today was about 5% out, on the same route I used to calibrate.