Tonga's indiscipline was a constant problem and Ganson finally lost patience after 24 minutes, sending Esikele Tonga to the sin-bin for yet another offence at the ruck.
Barkley played inside-centre in England's last two pool games, against Samoa and Tonga, but came off after 60 minutes in the Tonga game and was replaced by Farrell.
Like Samoa, both Fiji and Tonga have lost former heads of state in recent years: Ratu Sir Kamisese Mara, a former president of Fiji, died in 2004 and King Taufa'ahau Tupou IV of Tonga died in 2006.
Two Reihana penalties and a Soane Tonga'uiha try put Northampton further ahead before the Chiefs rallied.
Tonga took a 12-10 lead into the break, but the drama came in the second half.
The two sides of Tonga's brilliant stand-off Feleti Mateo were in evidence soon after.
Tonga has a particular problem among its female population with seven in 10 women obese.
Tonga coach Quddus Fielea said South Africa had underestimated them by fielding a second-string side.
Tonga captain Nili Latu hailed the team's improved discipline and confidence in their own game.
The extraordinary scene was captured along the Tonga Trench during a research expedition last summer.
Tonga's prime minister, Lord Tu'ivakano, says the courts will impartially consider a request for extradition.
The dead included 22 in American Samoa, 82 in Samoa and seven in Tonga.
Both should be fit for Saturday's game against Samoa, while Jason Robinson hopes to return against Tonga.
Boxers from Tonga are training in Liverpool as they prepare to take part in Olympic Games qualifiers.
His team-mates Phil Dowson and Soane Tonga'uiha are contenders, with Sarries duo Schalk Brits and Ernst Joubert.
This will assist to further build and connect the many on-going ESD activities already underway in Tonga.
The trench is a highly active fault line running north from New Zealand towards Tonga and Samoa.
The demoralised Dragons let Catt through for a walk-in try after a neat off-load from Tonga Lea'aetoa.
Those 12 are Argentina, Australia, England, Fiji, France, Ireland, Italy, New Zealand, Scotland, South Africa, Tonga and Wales.
The man also hurt his back when the 11.6m (38ft) vessel rolled after leaving Tonga two days ago.
His Digicel Group now operates in dozens of Caribbean islands, Honduras, Haiti, Fiji, Tonga and Papua New Guinea.
Billy Slater, Brent Tate, Cooper Cronk, Willie Tonga and Brett Morris all scored in a one-sided first half.
The 22-year-old will tour Fiji, Tonga and Samoa for three and a half weeks starting on 8 June.
Hull star Radford was part of the Federation Shield-winning England team that overcame a very physical Tonga side.
But Tonga'uiha had made it clear that he wanted to remain at Northampton.
Hola then added another three points before Tonga took the lead when Taione finished off a powerful forward drive.
Tonga, ranked four places below Samoa, reduced the deficit through a second Hola penalty as the half ended 12-6.
Between June and November, humpback whales congregate in Tonga to mate and breed.
But Wales were beaten 19-10 in the semi-finals by Canada, who lost to Tonga 14-12 in the Plate final.
On Tuesday, a magnitude 8.0 quake-triggered tsunami killed at least 111 people in the Samoan islands and Tonga.
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