Fiji had to come from behind in front of 4,500 enraptured spectators at Vichy's Stade Darragon to overwhelm Italy and win 43-17.
The South Sea islanders trailed the Italians 10-0 early on before scoring seven tries to ensure victory as the heat took its toll.
After a nervy opening dominated by the Italian pack Cagnoni's penalty got the Azzuri on the scoreboard before Derbyshire's try from a strong scrum put them 10-0 in the lead. However Waqa Etuate's men fought back, taking on the Italians with their own brand of physicality, and might have scored straight away had it not been for some handling errors. They did, though, score three tries to finish the half ahead.
Rabubawaqa went over after good work from Durutalo and then Tikoirotuma was put clear to score before Deryck Thomas' try ensured a 17-10 half time lead.
Italy's woes had barely begun, however, and before long Tikoirotuma had scored two more., At 31-17, Fijian victory was all but assured.
Derbyshire pulled one back for the Italians from the base of the scrum but, with the Fijians still attacking in relentless waves, Tikomainnaivalu touched down and Tikoirotuma rounded off a strong performance with his fourth try.
Quotes
Waqa Etuate, Fiji coach: I'm very pleased with this win even if we didn't play very well in the first 10 minutes. We had to win this match to set us up for the rest of the tournament. We want to finish in the top eight teams.
Jone Qovu Nailiko, Fiji captain: The group's come on and improved since our loss against Australia. We put some good passages of play together here and we hope that we can finish strongly and in a good position in the standings.