EXCLUSIVE BY CHRIS FOY: March 29 is not just Brexit day for Britain, it is also deadline day for rugby's unions to sign up for the Nations Championship.

The Principality Stadium roof will be left open for Wales' Six Nations Grand Slam game in Cardiff against Ireland, despite yellow wind warnings set for Saturday.

WILL KELLEHER'S SCRUM'S THE WORD: This week we have tales of Beards, beers, and Beirnes ahead of the biggest game of the weekend: Wales v Ireland, and plenty more besides.

If Ireland do not rain on Wales's parade, it is certain now that Storm Hannah will. With Gareth blowing through earlier in the week, it's Hannah's turn to wreak havoc.

WILL KELLEHER AT THE PRINCIPALITY STADIUM: Before the cascade of champagne to mark Wales' glorious Six Nations Grand Slam came the flood as they dominated Ireland.

The British and Irish Lions are in talks about staging a bumper international match against a top Test-playing nation at Twickenham ahead of the 2021 tour of South Africa.

Best suffered the damage to his left foot in Ulster's Champions Cup quarter-final defeat by Leinster on Saturday and following a scan on Monday it was confirmed he will be fit to lead Ireland in Japan

The fly-half has not appeared for Leinster since the turn of the year, and was ruled out of last Saturday’s Champions Cup quarter-final victory over Ulster with a quad issue.

The outgoing Wales coach was named head coach for the 2021 tour of South Africa on Friday, having already led the Lions to victory in Australia and a drawn series in New Zealand last time out.

Premier playmaker Johnny Sexton is expected to be fit shortly, but Ireland can ill afford to lose either of their main backline pivots. They open their World Cup by taking on Scotland on September 22.

England want all three available to take on Ireland to offset any need to pitch Billy Vunipola into a third Test in as many weeks. All three trained on Wednesday at England's Pennyhill Park camp.

Johnny Sexton has missed out on Ireland's World Cup warm-up clash with England at Twickenham on Saturday. The fly-half sat out of training at the start of the week in Portugal.

SIR CLIVE WOODWARD: It is exactly the team I would have picked for a must-win game at the tournament. This is the first time he has put his full strength side out in these warm-up games.

CHRIS FOY AT TWICKENHAM: The match tickets proclaimed 'this is no warm-up' and on a scorching, record-breaking day here, Manu Tuilagi and England proved too hot to handle.

Ireland and Wales will smash into each other in the final World Cup warm-up of the summer, despite the lingering risk of cruel last-minute injuries. Both sides are almost at full strength for Dublin Test.

Warren Gatland insisted that Rhys Patchell would travel to the World Cup on Wednesday despite suffering a worrying concussion in Wales' defeat to Ireland.

Fly-half Rhys Patchell will be assessed ahead of Wales' World Cup departure on Wednesday after he was concussed during their final warm-up game.

RORY KEANE: This Ireland squad were primed to reach a first-ever World Cup semi-final, and possibly more. But they have been seemingly in free-fall since the events of February 2 at the Aviva.

World Rugby bosses have hit back at claims 31-man World Cup squads threaten player welfare by insisting top coaches left their objections too late to have any effect for the 2019 tournament in Japan.

SCRUM'S THE WORD WORLD CUP DIARY: Rhys Carre, Wales fiery-haired loose-head prop, has one extra item in his bag - the 'Love Spoon'.

With the World Cup set to begin on Friday, nobody can predict which side will lift the Webb Ellis trophy on November 2. Sir Clive Woodwood has run the rule on every side in Japan.

Gregor Townsend confessed it 'doesn't look good' for Hamish Watson after admitting the Scotland flanker's World Cup might be over already. The Dark Blues suffered a 27-3 mauling from Ireland.

One week and 12 matches in the Rugby World Cup and we have our first rest day, which seems a natural time to take stock ahead of a jam-packed weekend. Here is our team of the week...

RORY KEANE IN SHIZUOKA: Carty starts only his second Test in place of conductor-in-chief Johnny Sexton, who is out with a groin injury. Schmidt reckons Carty has the right stuff.

With prop Demba Bamba out with a thigh problem, France announced on social media that Uini Atonio (below) would replace him. But they deleted the tweet after discovering he was injured.

Sexton captained Ireland for the first time on Thursday, but he was replaced by Jack Carty for the second-half of his side's five-try win over the Bears.

RORY KEANE IN FUKUOKA: Fourteen-man Ireland sealed their place in the World Cup quarter finals with a seven-try victory over Samoa here in Fukuoka, but Bundee Aki's red card will be a worry.

Bundee Aki was sent off in the 29th minute after a high tackle at Fukuoka Hakatanomori Stadium and faces a multiple-game suspension, souring the win that put Ireland through to the quarters.

Tadhg Furlong has warned that to switch off even for a second against New Zealand will cost Ireland the chance of a maiden World Cup semi-final.

SIR CLIVE WOODWARD: This game will be massive. So far in Anglo-Australian encounters at World Cups we have one victory apiece in the final, two England quarter-final wins and two Aussie pool wins.

Johnny Sexton has questioned the 'strange' negativity around Ireland's World Cup campaign, insisting Joe Schmidt's men are ready to peak for the All Blacks.

SCRUM'S THE WORD: South Africa star Cheslin Kolbe has warned that a new wave of pint-sized wingers are ready to explode into life at the World Cup.

'Sean aggravated a pre-existing neck muscle complaint and has been ruled out of the remainder of RWC19,' read an Irish Rugby Football Union statement.

The Rugby World Cup kicked off four weeks ago today and now, via 50 pool stage matches, we are down to eight teams. Sportsmail tells you all need to know about the quarter-finals.

Johnny Sexton has predicted that New Zealand will be cleaner in their Rugby World Cup quarter-final against Ireland following a bruising encounter in Dublin three years ago.

RORY KEANE IN TOKYO: Ireland have a shot at history here on Saturday, with the All Blacks standing in the way of a place in the World Cup semi-finals.

All Blacks take on Ireland in their Rugby World Cup quarter-final clash in Japan as they look to progress to the semi-final to take on either England or Australia. Follow LIVE ACTION RIGHT HERE.

Siya Kolisi succeeds Ireland fly-half Johnny Sexton as holder of the Pat Marshall Memorial Award after being recognised at the RUWC's annual dinner in central London.

RORY KEANE AT THE AVIVA STADIUM: Scotland head coach Gregor Townsend jumped to the defence of skipper Stuart Hogg for the incredible blunder which cost the visitors dear in Dublin.

RORY KEANE AT THE AVIVA STADIUM: Johnny Sexton says Ireland are trying to draw a line under the hellish events of last year and Saturday was a good start as Andy Farrell's side won.

SIR CLIVE WOODWARD: All eyes on England's next game against Ireland, and what a prospect that is. But I suspect history will show victory over the Scots to ultimately be more important.

Brian O'Driscoll has accused Eddie Jones of 'scaremongering' and admitted he relished the sight of the England head coach's comments backfiring so spectacularly against France.

WILL KELLEHER IN DUBLIN: The 59-year-old Bono dropped into the Irish camp to give a rallying speech to Andy Farrell's team ahead of their Six Nations clash with England.

During the Joe Schmidt era, Ireland were renowned for peppering the backfield with high balls from Johnny Sexton and Conor Murray but Eddie Jones insists that England can cope with it.

Conor Murray admits the father-son dynamic between the Farrells will be strange when Ireland face England on Sunday, but hopes his coach can provide crucial insights into his son's game.

Conor Murray admitted that the father-and-son dynamic between the Farrells will be strange when Ireland face England in the Six Nations.

SIR CLIVE WOODWARD: The good news is I sensed a sharpening of intensity with England at Murrayfield - but the bad news is some of Eddie Jones' selections are making me very nervous!

NIK SIMON'S FORM GUIDE: England have had an up and down Six Nations campaign so far, with one win and one loss, while Ireland are still undefeated at this stage.

DYLAN HARTLEY: A lot of people have been chucking stones at Eddie Jones but my message for the RFU is clear: give him a new contract. Dave at the pub might disagree.

MIKE BROWN: You always know when it's an Ireland Test week because the coaches put a life-sized cardboard cut-out of Johnny Sexton in the team dining room.