It would be longer than two miles Caroline. There is not a straight path from his back garden to WHF...He would have had to negotiate hedgerows and crops. The ruler needs to follow the fields edges where the paths are and I dare bet it is more than 3 miles...and in the dead of the night would be very difficult...OK he could have used a torch, but that might have seen and I doubt he would risk that.
He was a fit young man who probably ate all his carrots :D - I don't believe his movements would have been at all that difficult. Again, without his actual version we may never know his exact movements and can speculate till the cows come home, but it's clear there are many plausible possibilities - some not so plausible :D