At the 2013 Toronto Waterfront Marathon last Sunday, Ed Whitlock ran 3:41:58 setting a new record for an 82 year old. The previous record of 3:48:35 was set by Ed Benham in 1989.
Having started the race initially just faster than 8 min/mile pace, his pace began to slow around 15 miles and then more so at 20 miles. For the last 3 miles, his pace had dropped to about 10 min/mile pace before finally getting to the finish line in 3:41.
A short article about how he train can be seen in this earlier post.