According to Official Guinness Records,
The fastest marathon dressed as a love heart (male) is 3 hr 5 min 55 sec and was achieved by Joe Gale (UK) the Virgin Money London Marathon, in London, UK, on 22 April 2018.This was the eleventh year that Guinness World Records has partnered with the London Marathon.
For a complete list of 2018 records, please visit 2018 Guinness Records in United Kingdom.