Chelsea skated past the men from the Arctic circle and into the quarter-finals last night. Minus the snow which blighted the first leg, Tromso's defence simply melted away and Chelsea can now take a European break until March secure in the knowledge they really do have a great chance of winning this competition.

However, last night was not just about the contrast in the climactic conditions; it was also about the change that has come over Gianluca Vialli.

Last season he cut a sullen figure, often consigned to the bench and snubbed by the manager Ruud Gullit, who barely spoke to him. A fitness blitz in the summer has reawakened his hunger for the game and in response, Gullit has taken the Italian to his heart.

The change in the 33-year-old Vialli is amazing. Not only is he the club's top-scorer with 10 goals but as the final whistle went last night he and his manager were seen giggling together like schoolboys as Vialli left the pitch with the match-ball firmly tucked under his arm, reward for a hattrick which brings his tally to six in four European ties this season.

They include the two vital late strikes in the mud and snow of Tromso a fortnight ago which saved Chelsea's embarrassment in a game in which they could have conceded six had the Norwegians taken the inviting chances which fell their way.

Last night Chelsea were out to prove how well they play on the green, green grass of home, and though Tromso completed the last 35 minutes with only 10 men after Jonny Hansen was sent off for a second bookable offence, Gullit's side more than proved their superiority.

On 13 minutes Dennis Wise crossed from the right and Dan Petrescu, on the run, directed a glancing header past Tor Grenersen from close range for the opener.

And on 24 minutes Chelsea added a second goal which put them 4-3 ahead on aggregate. Di Matteo dispossessed Robin Bernsten, passed inside to Gianfranco Zola and Vialli completed the Italian connection by receiving his team-mate's pass and firing under the Tromso goalkeeper.

Chelsea looked to be applying an unbreakable grip on the game. But Tromso showed in the first leg they possess an indominatable fighting spirit as well as the ability to shoot from long range. Six minutes before half-time, a 20-yarder from Bjorn Johansen left Ed de Goey grasping at air.

However, the visitors had little time to celebrate the fact that they were level on aggregate again. Four minutes later Hansen committed a daft foul on Di Matteo just outside the Tromso area for which he was booked and Gianfranco Zola bent the freekick past Tor Grenersen to put Chelsea 3-1 ahead on the night.

Nine minutes after the restart it was 4-1. Zola's cross from the left found Petrescu in the Tromso area, the Romanian laid the ball back to Wise, whose shot at goal was handled by Hansen. The Norwegian was sent off for a second booking and seconds later Frank LeBoeuf scored from the spot.

Five minutes later Chelsea went 5-1 ahead on the night as Petrescu broke clear from deep in the Tromso half, arrived in the box and saw his shot partially blocked by a defender. However, the ball fell kindly to Vialli, who slotted home his second goal of the night.

His third and Chelsea's sixth came on 70 minutes when the Italian met Wise's right-wing cross with an unmarked header. Petrescu added the seventh from Zola's pass and Chelsea, unlike in the first leg, were home and dry.

Before the game, Vialli said he had a feeling this would be a great night for Chelsea. "But I didn't imagine I'd score a hat-trick," he admitted. Even Vialli's old adversary was singing his praises. "He's a great player," said Gullit, "a different player from last year. He's made me proud."