Hamilton took full advantage, bringing his car home 3.1 seconds ahead of Rosberg to close the gap to 22 points in the drivers’ standings with six races remaining.

Hamilton had conceded ahead of the race he could not afford to lose any more points to Rosberg with races running out.

The Briton could not have made a worse start though. He lacked power off the line, caused by an issue with his car’s race-start mode, and Rosberg comfortably held sway into the opening tight chicane of Variante del Rettifilio.

Hamilton dropped to fourth behind Kevin Magnussen in his McLaren and Felipe Massa for Williams, who along with team-mate Valtteri Bottas were confirmed as drivers with the team for 2015.

Hamilton’s woes at the start followed another problem 15 minutes before the race. With his mechanics working on the car on its grid slot, one of his team dropped a portable brake cooler on the front wing, breaking it slightly and forcing a change.

It was not the beginning he would have envisaged, but on lap five the fightback began as Massa ahead of him and Hamilton both passed rookie Magnussen in the space of 15 seconds.

With Rosberg’s lead just over four seconds at the start of lap nine, the German then outbraked himself into Rettifilio.

That forced him down the escape road through the chicane, swerving his way around the polystyrene blocks designed to avoid any driver straightlining the turns, losing around 1.7secs in the process.

A lap later, and with the bit between his teeth, Hamilton made his move on Massa into turn one to leave Rosberg in his sights.

As the duo traded fastest laps at one point, Hamilton was unable to get any closer than 1.2secs prior to the one and only stop – lap 24 for Rosberg, 25 for Hamilton, with the duo turned around equally.

At practically half-race distance – 26 of the 53 laps – Rosberg had eked out a cushion of 1.8secs, the duo on their own, with Massa a further 10 seconds adrift in third.

Despite Hamilton being told by race engineer Pete Bonnington to be patient and hold a gap of two to 2.5 seconds to Rosberg and attack at the end, Hamilton did not heed the advice.

On lap 27 he took half a second out of Rosberg and then 0.6secs on lap 28, before Rosberg was late on the brakes into Rettifilio at the start of lap 29, and again took the escape road.

That handed the lead to Hamilton, with cameras capturing a smile on the face of Mercedes boss Toto Wolff at that exact moment it happened.

It was a remarkable error of judgement from Rosberg – to make the same mistake twice seemed pretty unforgivable.

From that moment Hamilton was never troubled, coasting to the 28th victory of his career and making inroads into Rosberg’s points lead.

Behind them, Massa drove superbly to claim his first podium finish since last year’s Spanish Grand Prix, with Bottas fourth ahead of Red Bull duo Daniel Ricciardo and Sebastian Vettel in fifth and sixth.

It was a disaster of a race for Ferrari on home turf. Fernando Alonso retired on lap 29 and Kimi Raikkonen finishing a lowly ninth, sandwiching McLaren pair Jenson Button and Magnussen.

Ferrari have now dropped to fourth in the constructors’ championship behind Williams, with Red Bull out on their own in second, while Mercedes are fast closing in on the title with a lead of 182 points.

Marussia driver Max Chilton retired for only the second time in 32 races after hitting the kerb on the exit of the second chicane.

That sent him airborne momentarily, with his car landing heavily on the track and winding Chilton before his out-of-control car landed in a gravel trap before burying the nose in a tyre barrier.

A beaming Hamilton, in front of a sea of red along the start-finish straight as Ferrari fans crammed on to the track, said: ``What a great crowd!

“This is amazing to see, the whole start-finish straight is full of fans. You guys make this race, so thank you for your support.”

As for Rosberg, booed on the podium for the second successive race, he said: “It was a pity it didn’t work out today, but Lewis drove a great race so he deserves it.”

Trying to speak over the boos, Rosberg then spoke in fluent Italian, which appeased some at least.

Asked if they were friends again, Hamilton replied: “Of course, we’re team-mates, always will be.”

As for Massa, for so long a Ferrari driver prior to joining Williams this year, the Brazilian said: “I’m very happy for my first podium with Williams.

“From now until the last race we are there fighting, but I’m so happy to be fighting here, and there’s a lot more to come.

“You (the fans) are the best.”