Debut victory for dominating Porto.

Sebastian Porto had what could only be described as a perfect Rio Grand Prix - dominating from start to finish on his underpowered Yamaha despite tricky wet-dry conditions to take his debut Grand Prix victory after 104 starts.

Staring on pole for the first time in his Grand Prix career was Randy de Puniet, in what was his 61st GP start. However, the omens weren't looking too good for de Puniet having only finished twice in the last five races.

Starting next to the Frenchman would be the ever-impressive Sebastian Porto, making his sixth front row appearance this season. Porto, who recently celebrated his 24th birthday, made 100 GP starts without finishing in the top three, but since then has finished on the podium at three consecutive races.

Surprise of the Rio GP so far has been Toni Elias, who finished in 13th place in Portugal having crashed and re-started three times, but equaled his best ever qualifying position in the 250cc class in his debut year, while Marco Melandri is starting from the front row for the 11th time in 2002.

Not so impressive so far had been Elias' team-mate Fonsi Nieto, who failed to qualify on the front row for the first time since the South African GP, and with a championship at stake, needed to outperform Melandri today.

However, throwing a spanner in the works was the Rio weather, which turned 'ugly' this morning and the 125's had seen a wet race held on an increasingly drying track - but with random rain showers thrown in for added confusion, making tyre choice for the 250's all-important in weather conditions that could go either way.

Men to watch would surely be Brits Jay Vincent and Leon Haslam who had both been in the top six in the wet warm-up and were looking for revenge after being left devastated when they threw away a possible race victory in the wet at Estoril.

As the lights disappeared and the field charged into the dry looking turn one it was Porto who led the way and set off like a rocket, with Elias second, ahead of Rolfo, Melandri, Matsudo and Stoner - with the other side of the track much wetter.

Porto continued to pull away and had a lead of 2.4seconds - after just one lap! While by contrast Locatelli had made an appalling start and was now at the back of the field - had he gambled on a dry set-up..?

By lap 3 Porto had more good news when his pit board told him that he had a five second lead, but not so pleased was fourth placed Naoki Matsudo who was given a stop/go penalty for a jumped start.

In those early stages a distinct set of races were forming; Porto versus the racetrack for victory and Rolfo, Melandri, de Puniet, Elias, Matsudo, Battaini, Alzamora, Stoner and Vincent rounding out the pack

But more heartbreak was to follow for Vincent when his engine let go on lap 5, leaving the underpowered Cibertel rider to reluctantly pull off the racing line and into retirement.

Within 1 lap of Vincent's exit, Porto lead was up to an amazing 10secs in what is the Argentinean's closest thing to a home race. In terms of the championship, Melandri held fourth, five places ahead of his nearest title rival Nieto, who was being totaled outclassed by Toni Elias - who was now challenging Rolfo for second.

By lap 10 of the 22 a fully dry line was clearly visible all around the circuit, but such was the humidity that the speeds reached yesterday would never be repeated. While the pack fighting for second had started to spread out, with Melandri holding a 0.8secs lead over the battling Rolfo and Elias, with Porto still 8secs clear up front - but by no means safe.

The status quo at the front continued through the mid stages of the Grand Prix, with Porto out on his own (by 14 secs) and looking odds on for his first GP victory, with Rolfo holding a 2secs lead over Battaini, Melandri and Elias - who would soon have team-mate Nieto breathing down his neck, who himself was under pressure from Stoner and pole sitter de Puniet, who would crash out of ninth on lap 15.

But playing no further part was Roberto Locatelli, who had indeed bravely gambled on a dry set-up, only to be foiled by the constant drizzle sweeping the circuit. The Italian former 125cc World Champion pulled in to the pits and retirement.

Tragedy struck Nieto and his championship hopes mid way around lap 16 when he lost the front of his Telefonica liveried machine at the apex of a medium speed left hander - sending the Spaniard skidding into the gravel trap, whereupon his Aprilia flipped over and over, destroying itself.

Having checked the damage of his machine for himself the fuming Nieto then set out to vent his anger on various inanimate objects that included the tyre wall and various other expressions of disgust as he saw his title hopes frustratingly disappear into the Rio mist.

Fourth placed Melandri was soon given the news via his pit board, and the MS Aprilia rider would surely be on a points collecting exercise from then on as he sought top further bolster his huge points lead.

But back up front, Porto was looking as impressive as he had throughout as the laps wound down, and having not put a foot wrong so far the Petronas rider wasn't to be denied in the closing stages as his #9 machines 14 second lead stood firm to the finish.

Porto crossed the line with both hands punching the air with delight in a year when he had threatened to upset the order, but on more than one occasion had been let down by his machinery.

Joining the emotional Porto, who stopped to deprive a jubilant fan of his Argentine Football shirt on his slowing down lap, was Robby Rolfo who maintained his edge over Battaini, while Marco Melandri duly collected the points for fourth in what was mission accomplished for the Aprilia rider.

Full results to follow...

1. Porto
2. Rolfo
3. Battaini
4. Melandri
5. Elias
6. Stoner
7. Alzamora
8. Matsudo