Sapporo - Billy Vunipola knows he will be the cause of split loyalties when England open their 2019 Rugby World Cup campaign against Tonga in Sapporo on Sunday.

Not only are Vunipola's parents Tongan, his father Fe'ao, a hooker, and uncle Elisi, then the captain and fly-half, played for Tonga against England at the 1999 World Cup.

That match, which Billy watched, saw England enjoy a 101-10 win after Tonga had prop Ngalu Taufo'ou sent off after 35 minutes for punching.

Billy and brother Mako were raised in Wales after their father took up a contract with Pontypool. They were later educated in England and the latest generation of rugby-playing Vunipola brothers opted to represent the Red Rose.

"I am Tongan, my parents are and my grandparents are so it will be very emotional," said Billy Vunipola.

"I have to get my head right. With the country there will be split loyalties," the powerhouse No 8 added.

"They want Tonga to win and I want England to win."

Billy Vunipola will be the only member of his family involved in Sunday's match as Mako, an England prop, continues his recovery from hamstring surgery.

Tonga coach Toutai Kefu, when told Vunipola still felt Tongan, quipped: "Well he should be playing for us then."

Jones has picked his strongest available side for a match title contenders England are expected to win well against a Tonga team who only a few weeks ago suffered a 92-7 thrashing by reigning world champions New Zealand in a warm-up match.

But Jones said there was no question of taking Tonga lightly, hence a midfield trio of George Ford, captain Owen Farrell and dynamic centre Manu Tuilagi, with the likes of Vunipola and Maro Itoje powering the pack.

"I think World Cups are about always picking your strongest team, for that game," said Jones. "That's the only game we're worried about."

Jones is a seasoned World Cup campaigner, having been the coach of his native Australia when they lost the 2003 final to England before becoming a consultant to 2007 champions South Africa.

And four years ago he oversaw one of the great World Cup upsets when Japan beat the Springboks.

Yet for all his experience, Jones said: "I'm massively nervous and I'm massively excited.

"We control the preparation for the games and every coach -- all 20 coaches out here -- is having this conversation now. They all think they've done a great job preparing their team, but we don't know, do we?"

"I love it. If I didn't want that, I'd have a job where I could catch the bus at eight o'clock every morning, wear the same suit, take a briefcase and have my packed lunch," he added.

"I could do that and I'd probably do it pretty well, but I love this part of it: you work really hard to prepare a team and then you don't know what is going to happen."

Part of that preparation for what will be just the second rugby union match at the Sapporo Dome has involved speaking to the England football team that played and won there, 1-0 against Argentina, during the 2002 soccer World Cup.

"We spoke to members of that team and spoke about their experience at the ground. That all went into our preparation and planning for this game," said Jones.

"We spoke to Danny Mills, the defender."

Jones has never been adverse to pre-match 'mind games' and Kefu took a leaf out of his former coach's book when he said Tonga had "nothing to lose" and England were "under more pressure than us".

Kefu has selected a Tonga side where seven players are attached to English clubs.

Flyhalf Kurt Morath, Tonga's all-time leading scorer with 340 Test points plays for second-tier English team the Doncaster Knights, while captain Siale Piutau is at Bristol.

Teams:

England

15 Elliot Daly, 14 Anthony Watson, 13 Manu Tuilagi, 12 Owen Farrell (captain), 11 Jonny May, 10 George Ford, 9 Ben Youngs, 8 Billy Vunipola, 7 Sam Underhill, 6 Tom Curry, 5 Maro Itoje, 4 Courtney Lawes, 3 Kyle Sinckler, 2 Jamie George, 1 Joe Marler

Substitutes: 16 Luke Cowan-Dickie, 17 Ellis Genge, 18 Dan Cole, 19 George Kruis, 20 Lewis Ludlam, 21 Willi Heinz, 22 Henry Slade, 23 Jonathan Joseph

Tonga

15 David Halaifonua, 14 Atieli Pakalani, 13 Siale Piutau (captain), 12 Cooper Vuna, 11 Viliami Lolohea, 10 Kurt Morath, 9 Sonatane Takulua, 8 Maama Vaipulu, 7 Zane Kapeli, 6 Sione Kalamafoni, 5 Halaleva Fifita, 4 Sam Lousi, 3 Ben Tameifuna, 2 Sosefo Sakalia, 1 Siegfried Fisi'ihoi

Substitutes: 16 Siua Maile, 17 Latu Talakai, 18 Ma'afu Fia, 19 Dan Faleafa, 20 Nasi Manu, 21 Leon Fukofuka, 22 James Faiva, 23 Nafi Tu'itavake