I understand that they stopped runners at Gosford House/from going round Gosford House (?) after a certain time. There are several threads around on the whole issue, here and on Fetch.
Interesting - that was the bit I found the toughest as well. But surely you can't change the distance of a course that has been officially measured and has had a permit applied for? Wouldn't hat invalidate the permit to stage the race?
My run measured 26.49 miles on my Garmin, which even allowing for the margin of error, seemed to be a bit long.