Billy Vunipola joins Owen Farrell in missing England's World Cup opener

Vunipola, pictured, was sent to the sin-bin for a dangerous tackle on Andrew Porter in 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 games to three because of mitigating factors and the Saracens No 8 could shave an additional match off the total if he attends tackle school.

It means he will miss Saturday’s final warm-up fixture against Fiji at Twickenham and the pivotal World Cup opener against Argentina on September 9.

The decision comes the morning after Farrell was given a four-match ban for his dangerous tackle on Wales flanker Taine Basham on August 12 and is another grave setback for Steve Borthwick.

England’s head coach must now plan for the opener against Argentina without his captain and talisman as well as the only specialist No 8 in the squad.

Vunipola will be available for the clash with Japan in Nice on September 17 when he completes tackle school but Farrell will not be back until the final group games against Chile and Samoa.

At the video hearing held on Tuesday night, Vunipola admitted that his shoulder-led tackle that struck Porter on the head was a red card offence, triggering an automatic six-game suspension.

However, the hearing saw mitigation in his clean previous record, his immediate remorse and apology and the lack of aggravating factors, thereby resulting in a three-match reduction.

Tackle school – officially named the ‘coaching intervention programme’ – is allowed to be taken just once in each player’s career and is intended to modify the specific techniques and technical issues that lead to illegal hits.

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

“There’s no worrying about himself. He’s worrying about everyone else.”

While England’s build-up to the World Cup has been heavily disrupted by the disciplinary implosion that began against Wales – they received a total of three yellow cards and one red at Twickenham – and continued at the Principality Stadium, they can now formalise plans for the Fiji send-off and showdown with Argentina.

Borthwick names his team to face the dangerous Islanders on Thursday with Ben Earl likely to slot in at No 8 given that Tom Curry, another option in the position, is still struggling with an ankle injury.

England confirmed on Tuesday that Curry has yet to take part in full training as the influential Sale back row waits to make his first appearance of the build-up campaign.

With Vunipola and Farrell banned and Curry still in the treatment room, Borthwick must decide whether to make changes to his 33-man squad before the final submission date of August 28.