After having the same thoughts initially, I'm now pretty confident it's 5k, given the hills + my recent times elsewhere. I'm putting the ~4.8km gps watches give down to some weird gps/data related issue.
Definitely the largest discrepancy I've seen between gps and reality..!
Yeah I know, I did offer to go around with a wheel again but they didn't take me up on the offer..
Hahah could be some conspiracy to gain runners with an offer of guaranteed PBs