England’s Dylan Hartley may miss World Cup after receiving four-week ban

• Northampton hooker will not be available for first match of tournament• Hartley pleads guilty to headbutting Saracens’ Jamie GeorgeDylan Hartley faces missing the World Cup after receiving a four-week ban for striking an opponent with his head during Northampton’s Premiership play-off semi-final against Saracens. He will miss England’s three warm-up matches in August and September and the tournament opener against Fiji.The England hooker appeared before a three-man disciplinary committee in Coventry on Wednesday having been cited for confronting his opposite number Jamie George and leading w…