England will be without Dylan Hartley for their 2015 Rugby World Cup Pool A opener against Fiji after the Northampton Saints hooker was handed a four-week ban for an alleged headbutt during his side's Aviva Premiership semi-final defeat to Saracens.
The New Zealand-born forward clashed with Jamie George during the brutal 29-24 loss at Franklin's Gardens, appearing to strike his opposite number when retreating back from the opposition line following a strong driving maul that ended with a Tom Wood try.
George, a rival for Hartley's starting role at international level, reacted angrily while the latter was subsequently cited for the incident and called to attend a Rugby Football Union (RFU) disciplinary hearing in Coventry on 27 May.
"This offence falls within the low entry point for striking with the head," HHJ Sean Enright said. "There was no significant injury to the other party, the opposition player was not removed from the field of play and the incident did not affect the game. However, there cannot be any place in our game for this class of behaviour, and that is why we have imposed this sanction."
The suspension is due to begin on 15 August, meaning that the player will be unavailable for England's three warm-up tests against France and Ireland as well as the World Cup curtain-raiser at Twickenham on 18 September.
This is certainly not the first time that Hartley's ill-discipline has landed him in hot water. In 2013, the 29-year-old was denied a place in the British and Irish Lions touring party for Australia after being handed an 11-week ban following a red card in that year's Premiership final.
He was ruled out for six months in 2007 due to gouging, eight weeks in 2012 for biting Ireland's Stephen Ferris during a Six Nations fixture, and missed another fortnight later that year following an altercation with Ulster's Rory Best.
Hartley was also banned for three weeks in December 2014 after being adjudged to have elbowed Leicester Tigers centre Matt Smith.
Stuart Lancaster has previously pledged to hold a discussion with Hartley, who was named in England's 50-man training squad announced earlier in May, over his discipline, although it remains to be seen if this latest transgression will have any impact on his long-term thinking.