According to Official Guinness Records,
The fastest half marathon carrying a 20-lb pack is 1 hr 31 min 25 sec and was achieved by Andrew Tarrant (UK) at the Brooks Fleet Half Marathon in Fleet, UK, on 20 March 2016. Andrew applied for this record in 2014 but, after dislocating his right knee, had to postpone until now. He wanted to prove that 9-5 office workers can achieve "big things".
For a complete list of 2016 records, please visit 2016 Guinness Records in United Kingdom.