The thing about The Sea Wall is it was....'a sea wall'.
It was not a footpath or driveway that was attached to main roads or other pathways. It was not a route or short cut to anywhere.
It was also dark and secluded. Not a safe place to be at night.
Absolutely no reason why anyone would be on it from sunset to sunrise. Not exactly Waterloo Station during the day either.
The route is straight, flat, in the open, has good terrain and does not go within 50 yards of any properties. He also knew the route.
Worth the risk.