Born Rebecca Mantin on 18 October 1980 to Wendy and Richard Mantin in Norwich, Norfolk, Mantin grew up in the south Norfolk village of Saxlingham Nethergate and attended Norwich High School for Girls and the Sixth Form atNorwich School.
Mantin started her media career writing for the Eastern Daily Press and appearing on the commercial radio station Broadland 102. She then moved to ITV Anglia, initially as a fashion presenter for lunchtime magazine show Home Malone before undertaking meteorological training to become ITV Anglia's main weather presenter, later presenting and reporting on regional programmes including the consumer show Late Night Checkout and animal rescue series 'Animal Tales'.
Mantin then started to appear on the national ITV Weather, Channel 5, Sky and This Morning on ITV as a reporter. From 25 February 2005 she ceased duties with ITV Anglia and joined ITV Weather on a permanent basis. She co-presented ITV's This Morning Summer with Denise van Outen and Richard Bacon in summer 2005 to celebrate 50 years of ITV.
Mantin married former yachtsman turned professional rugby coach Jack Heald in Walberswick on 12 December 2009. Mantin gave birth to a boy in October 2010. Her second son was born in May 2012.
A keen surfer, whilst dating BBC Sport commentator Dan O'Hagan, Mantin was struck in the head in a surfing accident on 7 June 2007 in Cornwall. She was pulled out of the water and initially rushed to hospital with concussion and memory loss. While at her parents' home in Norwich a week later, she collapsed and was rushed to hospital for a brain scan before checking herself out more than three weeks later. Mantin returned to ITV screens on 23 August 2007, although she was still experiencing dizzy spells and severe migraine and was signed off work again only to return to full-time presenting early in 2008.