Get a Telegraph Sport subscription for £1 per week Eddie Jones has vowed to stay on as England head coach after Saturday’s humiliating World Cup final defeat to South Africa, with the RFU planning to open talks over extending his contract until the end of the 2023 tournament. Jones’ current deal expires in August 2021 and the Australian is adamant he will not walk away despite his England side, heavy favourites before the match, producing arguably the worst performance of his tenure in their comprehensive 32-12 loss in Yokohama. The 59-year-old repeatedly refused to commit himself beyond the end of that deal when asked on Saturday night, but RFU chief executive Bill Sweeney on Sunday gave…