Dylan Hartley could single-handedly derail England's World Cup hopes if the Northampton hooker's disciplinary record does not improve, according to former coach Sir Clive Woodward.
Hartley earned the second red card of his chequered career after elbowing Leicester centre Matt Smith on Saturday 20 December and faces another ban from the game, which could rule him out for the start of the Six Nations championships against Wales in Cardiff.
The Saints forward's ill-discipline, which led to his yellow card in the autumn loss to South Africa, has been a constant theme of his club and international career and with the World Cup on the horizon Woodward believes coach Stuart Lancaster faces a big decision.
"Dylan Hartley is one of the hardest men for England and Northampton but he must be coached how to handle himself if he is going to be trusted in key World Cup games," 2003 World Cup-winning head coach Woodward told The Daily Mail.
"It is one thing to be sent off in a league game, a Six Nations match or an Autumn International, but to see red in a key World Cup game would be unforgivable.
"Hartley is England's No 1 hooker and you want him in your side, but not at the risk of him blowing a once-in-a-lifetime opportunity — to win the World Cup on home soil.
"He must take responsibility and so must Stuart Lancaster. If Hartley can't be trusted to keep his cool, he doesn't play."
The 28 year old is one the more experienced members of Lancaster's squad, having won 61 caps, while he started each of the Tests against New Zealand, South Africa and Australia in November.
Though Hartley has had four separate lengthy suspensions from the game, amounting to 47 weeks out of action, the England man has also been the victim having been eye-gouged by Richie Rees in the 2011 Six Nations, leading to an attack by Wales coach Warren Gatland.
And ahead of the Six Nations championship curtain-raiser on 6 February at the Millennium Stadium between Wales and England, Woodward warns Hartley he will have to contend with being targeting by the ex-British and Irish Lions coach.
"Hartley needs support and, with his poor disciplinary history, there will be no hiding place when he is scrutinised in the media," Woodward added.
"Lancaster has to make some big calls ahead of the opening Six Nations match against Wales — which is huge — but, if available, I would pick Hartley.
"He will be targeted and Wales coaches Warren Gatland and Shaun Edwards will try to get under his skin. Gatland has tried to wind up Hartley before and he has experienced players in his squad who will try to light his fuse during the game."