After two days of roasting hot weather, dominated by Dani Pedrosa, rain arrived on Sunday, giving the underdogs a welcome chance to shine and increasing pressure at the front of the field - particularly when Pedrosa and second-on-the-grid Valentino Rossi were only 13th and 17th in the wet warm-up.

Meanwhile Stoner, who had struggled to a season's worst ninth in qualifying and needed to beat Rossi to wrap up the crown, had been an impressive second fastest in the warm-up - and charged up to third by the end of lap one.

Pedrosa defied his warm-up performance to snatch an early lead, and the Repsol Honda rider even made a slight break - before being reeled-in by wet weather specialist Anthony West. Unfortunately for the Kawasaki rookie, he had jumped the start and was given a ride-through penalty almost exactly as he passed Pedrosa for the lead on lap 2 of 24.

When West pulled into the pits a lap later, fellow Australian Stoner - having overtaken Pedrosa - inherited the advantage, but held it only briefly before being passed by Marco Melandri. The Gresini Honda rider had led the wet warm-up, charged quickly forwards from ninth on the grid and continued to lead until just after the halfway point.

Stoner had stuck to Melandri's rear wheel, but it was Rossi who eventually toppled his fellow Italian. The Doctor had dropped back to seventh on the opening lap, then made steady progress forwards and, as the track developed a clear dry line, was able to hunt down and pass title rival Stoner on lap 12.

Rossi's determination to take the lead almost saw him collide with Melandri, whom he had left hospitalised after a Motegi collision in 2005, but the #46 made a clean out-braking move stick at the end of on lap 14 - after which Melandri and Stoner immediately dived for the pits, with Rossi waiting one further lap.

The circuit was effectively dry by that stage and, with lower ranked riders gambling on a bike change much sooner, lap times proved that slick tyres were the way forward. Stoner, Melandri and Rossi were ultimately punished for staying out so long, since all three missed out on a podium, but few could blame them - Stoner and Rossi were concentrating on beating each other, while Melandri probably found it hard to surrender the grand prix lead.

When the order had sorted itself out, Capirossi had taken the lead - helped by a perfectly timed bike swap - with Kawasaki's Randy de Puniet, who had run off track while third in the early stages, in second place ahead of Melandri's team-mate Toni Elias and the Dunlop Yamaha Tech 3 of Sylvain Guintoli! Stoner and Melandri were fifth and sixth, but Rossi was down in 11th.

The Italian's problem wasn't the timing of his pit stop, since he rejoined in second behind Capirossi, but some form of issue with the front tyre of his second Fiat Yamaha, which prompted the former five times MotoGP world champion back into the pits to have his machine examined - all but handing Stoner the crown. Rossi was sent back out, but again struggled to slow his M1 - running wide at the end of the back straight - and he was left to limp home in a very unlucky 13th.

Meanwhile, Capirossi was never under threat and charged to his third Motegi victory in a row by over ten seconds from de Puniet, who in turn claimed his first ever MotoGP podium by 1.5secs over Elias. Toni, still recovering from a broken femur, was forced to hold off a spirited attack by class rookie Guintoli to secure his second podium of the season - but will it be enough to keep his Gresini seat for 2008?

After an unsuccessful lunge at Elias, Guintoli was forced to settle for a career best fourth - a comfortably 16secs clear of long-time leader Melandri, who had overtaken Stoner on lap 20. Casey was probably pleased to have his future team-mate away from his rear wheel and went on to cross the line a safe sixth, almost 20 seconds clear of West.

After claiming his place in MotoGP history, a relieved Stoner was congratulated by both outgoing champion Nicky Hayden and 2001-2005 champion Rossi, before carrying a huge Australian flag back to the pits - where he was mobbed by an erupting Ducati team, ready with 'world champion' winning t-shits. After the podium ceremony, Stoner and his crew were quite rightly allowed onto the rostrum to celebrate their triumph, claimed at the home circuit of rivals Honda, Yamaha, Kawasaki and Suzuki.

Indeed, Ducati is the first non-Japanese manufacturer to win the premier-class crown since Phil Read handed another Italian factory, MV Agusta, its final 500cc World Championship in 1974. Stoner is the second youngest world champion after Freddie Spencer in 1983, while Bridgestone's first MotoGP World Championship ends Michelin's 14-year reign.

Stoner's former 250cc rival and fellow 21-year-old, Pedrosa, a pre-season title favourite, had a much worse day - suffering a vicious highside out of the final turn, while on worn wet tyres, on lap 15.

Stoner will now take his first world championship home to Phillip Island in Australia, on October 14.

Japanese Grand Prix:

1. Capirossi
2. de Puniet
3. Elias
4. Guintoli
5. Melandri
6. Stoner
7. West
8. Barros
9. Hayden
10. Hopkins
11. Vermeulen
12. Tamada
13. Rossi
14. Edwards
15. Ito
16. Nakano
17. Yanagawa
18. Checa