No. 8 Vunipola joins Farrell in being banned for England's World Cup opener

Vunipola was initially sent to the sin-bin for a dangerous tackle on Andrew Porter during Saturday's 29-10 defeat in Dublin, but the offence was upgraded to a red by the bunker review system.

An independent disciplinary hearing reduced the entry-level ban of six weeks to three because of mitigating factors and Vunipola, the only No. 8 in England's World Cup squad, will have another week removed if he attends World Rugby's 'tackle school'.

The 30-year-old Saracens back-rower is now ruled out of England's final warm-up fixture against Fiji at Twickenham on Saturday and their key tournament opener with Argentina in Marseille on September 9.

Wednesday's announcement by the Six Nations, which oversees disciplinary matters for some tournament warm-up games, comes the morning after Farrell was given a four-match ban for his dangerous tackle on Wales flanker Taine Basham on August 12.

Vunipola will be available for the Pool D match against Japan in Nice on September 17, but fly-half Farrell will not be able to be selected by England coach Steve Borthwick until his side's final group games in France against Chile and Samoa.

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During a video hearing held late on Tuesday, Vunipola admitted his shoulder-led tackle to the head of Porter was a red card offence.

That in turn triggered an automatic six-game ban.

- 'Immediate apology' -

But a three-strong panel including former Scotland coach Frank Hadden, found mitigation in Vunipola's previously clean record, his immediate apology and the lack of aggravating factors, with the result that the ban was effectively cut in half.

"The player admitted that he had committed an act of foul play worthy of a red card," said a statement issued on behalf of the disciplinary committee.

"On that basis, the committee applied World Rugby's mandatory minimum mid-range entry point for foul play resulting in contact with the head. This resulted in a starting point of a six week suspension.

"Having acknowledged mitigating factors including his exemplary previous record, immediate apology and remorse, and noted the absence of any aggravating factors, the committee reduced the six week entry point by three weeks."

'Tackle school', officially known as the coaching intervention programme, can only be attended by a player once in a career and is designed to iron out the faults that lead to dangerous tackles.

"Billy has been through a lot in his career and has been really mature and really helpful towards the rest of the squad," said England attack coach Richard Wigglesworth.

"There's no worrying about himself. He's worrying about everyone else."

Ex-England captain Borthwick is due to name his side to play Fiji on Thursday.

Ben Earl is set to start at No. 8, with Tom Curry, another alternative in the position, still struggling to overcome an ankle injury.

With Farrell, Vunipola and Curry all still sidelined, Borthwick must decide whether to alter his 33-strong World Cup squad before the closing submission date of August 28.

Farrell was suspended after World Rugby won their appeal against the controversial decision to overturn his red card -- a move that sparked widespread criticism throughout the game.