According to Official Guinness Records,
The longest front flip measured 6 m 18 cm (20 ft 3.31 in) and was achieved by Drew Taylor (UK) on the set of ‘Officially Amazing’ (CBBC) at NDGA Gymnastics Club in Tunbridge Wells, UK, on 15 August 2014.
For a complete list of 2014 records, please visit 2014 Guinness Records in United Kingdom.