Leicester wing Varndell scored an impressive brace for England
England began their World Sevens bid in Dubai with a 42-5 win over Hong Kong.
They fell 5-0 down after Kevin Barrett was sin-binned but scored five tries after the break, Tom Varndell with two.
Varndell, back in an England Sevens shirt for the first time since the 2006 Commonwealth Games, sprinted 80 metres to score with his first touch.
Wales opened the tournament with a 31-5 win against Zimbabwe, Scotland lost to Canada 33-14, while Ireland took the lead against Samoa, before losing 35-5.
For England, Ben Gollings scored twice to finish with a personal haul of 22 points while Josh Drauniniu crashed through two tackles to get his name on the scoreboard.
The Wales match featured a hat-trick for Craig Hill, but ended in controversy after the referee blew for time 30 seconds early.
PREVIOUS RWC SEVENS WINNERS
1993 in Edinburgh: England (beat Australia 21-17 in final)
1997 in Hong Kong: Fiji (beat South Africa 24-21 in final)
2001 in Argentina: NZ (beat Australia 31-12 in final)
2005 in Hong Kong: Fiji (beat New Zealand 29-19 in final)
Wales coach Paul John, looking ahead to qualification for the quarter-finals was furious with the early finish and said: "Points difference could be very important in this competition."
Colin Gregor scored both Scotland tries in the second half but could not stop a dominant Canadian side.
Brian Tuohy opened the scoring for Ireland but a Rupena Levasa hat-trick ended their chances.
Test winger Julien Malzieu was among the scorers as France beat the United States 26-17 in a fiery encounter which saw Todd Clever sin-binned for punching.
England squad: Kevin Barrett (Exeter); Tom Biggs (Leeds); Chris Cracknell (Exeter); Isoa Damudamu (British Army/Wasps); Josh Drauniniu (Royal Navy/Exeter); Ben Gollings (Gold Coast, Australia); Ollie Phillips (captain, Newcastle); James Rodwell (Moseley); Charlie Simpson-Daniel (Gloucester); Tom Varndell (Leicester); Rob Vickerman (Leeds); Andy Vilk (Treviso).
Ireland squad: Kyle Tonetti, Eoghan Grace, James Coughlan, Paul Marshall, Kieron Campbell, Felix Jones, Brian Carney, Brian Tuohy, Conan Doyle, Tom Gleeson, Daniel Riordan, Gary Brown.
Scotland squad: Colin Gregor (captain, Glasgow), Mike Adamson (Glasgow), Rob Dewey (Ulster), Andrew Easson (Edinburgh), Scott Forrest (Ayr), Roddy Grant (West of Scotland), Rory Hutton (Hawick), Roland Reid (Edinburgh), Scott Riddell (Blaydon), Colin Shaw (Glasgow Warriors), James Thompson (Edinburgh), Andrew Turnbull (Edinburgh).
Wales squad: Lee Beach (capt, Neath), Rhodri McAtee (Cornish Pirates), Lee Williams (Scarlets), Tom Isaacs (Newport), Aled Thomas (London Welsh), James Merriman (unattached), Tal Selley (Dragons), Aled Brew (Dragons), Craig Hill (Newport), Rhys Webb (Ospreys), Richie Pugh (Exeter), Dafydd Hewitt (Blues).