The fastest marathon dressed in a full suit is 3 hr 24 min 46 sec and was achieved by Paul Buchanan (UK) at the Lifestyle Sports - adidas Dublin Marathon, Dublin, Ireland, on 26 October 2009.
Paul wore a jacket, waistcoat, shirt, tie and trousers purchased for £50 specifically for this record attempt. He ran to raise awareness for Chrohn's Disease, from which his sister-in-law suffers. The time in the record is Paul's "chip time." Chip time differs from "finish time" in that it is measured by the electronic chip given to all racers that calculates exact time from crossing the starting line to the finish line. This eliminates the excess time incorporated in "finish time" (aka "gun time"), for example the time spent by a runner waiting to get to the official starting line after the marathon has begun.
Comments below may relate to previous holders of this record.