Quite. But having since checked "The Ghost Runner" (great book if you've not read it), they used to run 50- and 100-mile races around tracks, so I'm guessing 26 and a bit would be a relative doddle. Just interested to see the comparison in times, really.
That answers a question I was going to ask, namely could someone set a marathon record around a standard 400m track? Given the 'rules' above that's a no-no, but it would be interesting to see how long it would take someone to complete 26.2 miles of the same course, and compare the time with that...
If you extrapolate it further back, how long did it take to cut the same amount of time before 1985? I reckon it could be fewer than 28 years, but nearly four minutes is a lot to lose over 26.2 miles. I'd love to see it though.