The 32-year-old hooker has not played for his club since suffering concussion in the Six Nations defeat by Ireland at Twickenham last month which secured the Grand Slam for the Irish.
“I’m very disappointed that I will not be available for selection for Saints’ remaining Premiership games, as well as England’s tour to South Africa,” said Hartley.
“It has been recommended by specialists that I take a break this summer and while I find that decision hard to accept, it’s important I listen to that advice.
“I intend to use this time to recover fully from my injury, so I can be ready to hit the ground running when pre-season training starts later this summer.”
England's tour to South Africa is starting to look much tougher than first thought.— Ali Stokes (@alistokesrugby) April 23, 2018
Potentially, England could be missing...
We'll see which Lions Jones decides to rest & whether Billy is fit.
Hartley’s unavailability adds to England head coach Eddie Jones’s headaches as he tries to get England back on a winning track after an underwhelming defence of their Six Nations crown.
England are on a losing run of three ahead of the three Test series and will be without other key players such as Baths backs Anthony Watson, who has an Achilles injury, and Jonathan Joseph, who needs foot surgery.
Knee injuries, meanwhile, look set to remove lock Courtney Lawes and number eight Nathan Hughes from the tour which includes Tests on June 9, 16 and 23.
England last toured South Africa in 2012 losing the first two Tests before drawing the final match.
The Blues will face Gloucester, who defeated Newcastle 33-12 on Friday night, at Bilbao’s San Mames Stadium on May 11 following a pulsating Arms Park clash that went their way 16-10.
The home side emerged victorious despite Pau enjoying sustained scrum dominance that saw them gain several penalties from referee John Lacey.
But the Blues, Challenge Cup winners in 2010, held their nerve as full-back Gareth Anscombe scored an early try, while Wales fly-half hopeful Jarrod Evans kicked three penalties and a conversion.
Pau’s World Cup-winning former New Zealand centre Conrad Smith touched down for the visitors, with fly-half Tom Taylor adding a conversion and penalty, but the French side ultimately suffered their first defeat in this season’s competition.
They had breezed through the pool phase by collecting 29 points from a possible 30, yet the Blues proved tough nuts to crack as young talents like Evans, lock Seb Davies and flanker Ellis Jenkins all delivered performances of impressive maturity.
And the Welsh challengers dug deep during an intense second period that produced just three points before claiming a showdown in Spain against Gloucester.
The Blues made a flying start as they breached Pau’s defence inside six minutes.
Evans was the catalyst, rifling out a defence-splitting pass to lock Davies, who then timed his delivery perfectly to an unmarked Anscombe and the Blues were off and running.
Evans converted from the touchline and Pau – despite some early impressions in the loose by their juggernaut forwards – found themselves seven points adrift.
Great to see the whole Cardiff Blues squad together in the Arms Park clubhouse this evening, enjoying each other’s company. It’s probably the tightest group I have known in 25 years covering the club. And that’s key to the success they are now enjoying.— Simon Thomas (@simonrug) April 21, 2018
The setback, though, did not deter them in terms of applying relentless scrum pressure, and after Taylor missed a 17th-minute penalty, they drew level by capitalising on an Anscombe error.
The Wales international’s attempted clearance from just outside his 22 was charged down by Pau lock Julien Pierre, and although Pierre could not gather, Smith kicked on and won the race to claim a try that Taylor converted.
Evans then kicked a penalty to edge the Blues back in front, and although Taylor landed an equalising strike, Evans came up trumps again two minutes before half-time as his team shaded a fierce first half 13-10.
Pau captain Thibault Daubagna missed with a long-range penalty attempt early in the second period and Pau – marshalled superbly by their midfield general Smith – began to show some attacking prowess.
But the visitors could not make it count in the Blues’ 22, and Evans made them pay when he kicked a 40-metre penalty six minutes from time and sparked celebrations for an 11,700 crowd.
Major League Rugby, the latest attempt at launching a top-flight rugby union league in the United States, kicked off its inaugural season Saturday with confidence of a long-lasting impact.
The Glendale Raptors of suburban Denver downed visiting Austin Elite 41-26 and NOLA Gold of New Orleans defeated the host Houston SaberCats 36-25 in the openers of the seven-team circuit’s 10-week regular season.
“Following two years of challenging background work to lay the foundation for MLR, we finally get to see the fruits of our labor,” Raptors general manager Mark Bullock said in a posting on the MLR website. “It’s better than we can imagine.”
The San Diego Legion will visit the Seattle Seawolves on Sunday. The Utah Warriors debut next week and a New York expansion team opens in 2019.
“Years from now, people will be looking back on this opening weekend of Major League rugby as the notable inflection point that would fuel American rugby’s emergence on to the world stage,” said Warriors general manager Kimball Kjar, a former USA Eagles scrum half.
“Those may seem like very heady words but the commercial and athletic potentials of the American sports market, as they pertain to rugby, will only be realized with a smart and scalable business approach to professional rugby like the MLR.”
MLR uses a single-entity model similar to that of Major League Soccer, teams sharing ownership in the league. Each has a $350,000 salary cap with ESPN and CBS Sports as telecast partners.
“We fully expect the quality of play will be awesome and the excitement will build across the MLR season,” SaberCats co-founder Jeremy Turner said.
MLR follows a failed 2016 attempt to establish a US league, with PRO Rugby lasting only one season with five clubs.
“MLR is grateful to PRO, and to anyone else who have invested time and energy to grow the American game,” an MLR spokesman told AFP. “Ultimately, MLR believes in its model because it draws on the strength of American rugby and its existing infrastructure in a way those that came before us did not.”
The US rugby community and private investors provide an elite home outlet for USA Eagles talent such as Todd Clever, the former US captain who is the most capped American in history.
In 2009, Clever became the first American player in Super Rugby with the South African Lions squad, He also played for the Newcastle Falcons in the 2015-16 English Premiership campaign.
But on Saturday, at age 35, he took the field for Austin and after the game tweeted, “I try, I try and I try again. This game is just too much fun!”
Clever has helped with player recruitment and to boost off-field support for MLR.
“I have really enjoyed the business side of rugby, and I thought my playing days were over, but I do have a rubber arm when it comes to playing,” Clever said in a posting on the Elite website. “To be part of Major League rugby as a player is really special.”