Felipe Massa kept the championship alive with second place after his Ferrari team mate Kimi Raikkonen let him pass but
Robert Kubica's slim hopes of winning the title disappeared despite the Pole making a sterling effort to get his BMW-Sauber up from 11th on the grid to sixth at the finish.
There were no mistakes on Sunday, and no repeat of the
McLaren's Heikki Kovalainen tried to help his team mate with a vain attempt to force his way past
Twice world champion Alonso, who won the last two races, quickly regained fourth place from Kovalainen and held it to the finish.
By the time of his second stop, he had built up a sufficient advantage to comfortably return to the track with his lead intact and he crossed the line nearly 15 seconds ahead of
Brazilian Massa had been running third a substantial distance behind Raikkonen but the world champion slowed to let his team mate past seven laps from the end.
Kubica's German team mate Nick Heidfeld was fifth, his compatriot Timo Glock seventh for
Kovalainen's 27th birthday was ruined by a run onto the grass on lap 35 which resulted in puncture to his front right tire and he retired in the pits a few laps later.