“It’s unbelievable. Just unbelievable,” he kept mumbling at no one in particular.

The 23 year-old had begun uttering that word, in a rather higher register, while choking back tears on his victory lap an hour earlier.

“You’re the world champion,” Red Bull’s team principal Christian Horner had screamed. “You are the man.”

“Thank you guys,” Vettel had stammered in reply. “Unbelievable. I love you.”

Inside the helmet, his brain was desperately trying to process what had just taken place.

“To be honest I did not know anything,” Vettel recalled later. “In the last 10 laps, my engineer Rocky (Guillaume Rocquelin) was giving me advice to help me get the car home. I wondered why he was so nervous. I thought we must be in a good position. Then he said 'it's looking good', I didn't know what he meant. I just focused on myself, and then they came on the radio and screamed that we have won the world championship. I’m speechless.”

To be honest, it was fairly unbelievable; an extraordinary end to an extraordinary season.

That Fernando Alonso, who with Vettel’s team mate Mark Webber behind him needed only to finish fourth to be sure of securing his third world crown, should fall victim to a disastrous decision by his team Ferrari and spend the race stuck behind the Renault of Vitaly Petrov.

That Vettel, who had never once led this year’s championship - or any Formula One championship for that matter - until Sunday, should emerge victorious.

That he should have come from 25 points behind with two races remaining.

Ferrari will be kicking themselves. For all the talk of team orders, for all the questioning of Alonso’s worthiness to call himself a champion, the Spaniard had been utterly brilliant in the second half of the season.

Yes, the governing body was wrong not to dock him the seven points he won at Hockenheim when Felipe Massa was ordered to make way for him, but if he had triumphed on Sunday his victory would have met with grudging respect even from his greatest detractors.

The Spaniard was inconsolable at the end, sitting at the back of his team’s motor home in stunned silence.

Maybe he should have seen it coming. From the moment German newspaper Bild dropped a banana skin in front of his car on the grid for a contrived photo opportunity, nothing went Alonso’s way. Spain's attendant King, Juan Carlos, seemed to sense it too, admonishing Martin Brundle for suggesting that his subject was the title favourite. “It’s bad luck,” he said.

So it proved. Starting third, Alonso ignored his team’s instructions to keep his car on the clean side of the grid, instead swerving to try to cut off McLaren’s Jenson Button. The Englishman reached the first corner in the lead.

Still, Alonso was set fair. As a safety car came out following Michael Schuamcher’s near decapitation at the hands of Force India’s Tonio Liuzzi, the Spaniard held fourth place. With Webber behind him in fifth, it would have been enough.

It all went wrong following the restart when Webber pitted complaining of rear tyre degradation. Ferrari decided to ‘cover’ him as their nearest challenger, and Alonso dived in soon after. It was the key moment in the race. Emerging in 14th, just ahead of the Australian, Alonso found himself in traffic behind Petrov. He never made it past the Russian. Renault, whose fragile engine has cost Red Bull at crucial times this year, finally came through for the Milton Keynes-based team.

It was left to Vettel to control the race from the front. And whatever his critics may say about his racing ability, there is no question mark over Vettel’s ability to do that.

McLaren's Lewis Hamilton, who retained an outside chance of the title if he could win the race, was his only serious challenger. But after pitting on lap 23 the Englishman emerged behind Renault’s other challenger, Robert Kubica. There was no way past. The Pole did not stop until lap 46, by which time Vettel, whose own pit-stop on lap 24 had been lightning quick and had got him out in front of Kubica, had a 13-second cushion.

At 23 years and 135 days, Vettel had just usurped Hamilton as Formula One’s youngest ever world champion by 166 days.

Red Bull’s celebrations were raw, epic and tinged with sadness. The heart went out to Webber. The Australian arrived at this jewel in the desert on Alonso’s shoulder, confident he could capture his maiden title at the age of 34. He deserved to after a season in which he has battled heroically. It was not to be.

After a while spent collecting his thoughts up in Red Bull’s motor home, Webber came out and congratulated his team mate, promising him he would be back to take it off him next season.

“Well done to Seb,” he said. “It goes on.” Does it go on, he was asked? “Yes.” Thank God for that. The sport would be the poorer without him.

In the end, though, no one could argue that Vettel did not deserve his title. The man hailed as “Baby Schumi” by the German press after becoming Formula One’s youngest ever race winner at Monza in 2008 has been in unstoppable form in the latter part of the year.

He took a total of 135 points in the final nine races of the year, including three victories in the last four races. It would have been four from four but for an engine failure 10 laps from the end in Korea.

“This race started in daylight and I think it’s going to end in daylight too,” he grinned when asked how he would celebrate. “I am speechless. It is unbelievable.”

Just at that moment someone strolled past wearing a T-shirt bearing the legend: “Vettel: 2010 world champion”. Clearly not everyone was so surprised.

Abu Dhabi GP result:

1 Sebastian Vettel (Ger) Red Bull 1hr 39mins 36.837secs
2 Lewis Hamilton (Gbr) McLaren 1:39:46.999
3 Jenson Button (Gbr) McLaren 1:39:47.884
4 Nico Rosberg (Ger) Mercedes GP 1:40:07.584
5 Robert Kubica (Pol) Renault 1:40:15.863
6 Vitaly Petrov (Rus) Renault 1:40:20.357
7 Fernando Alonso (Spa) Ferrari 1:40:20.634
8 Mark Webber (Aus) Red Bull 1:40:21.080
9 Jaime Alguersuari (Spa) Scuderia Toro Rosso 1:40:27.038
10 Felipe Massa (Bra) Ferrari 1:40:27.705
11 Nick Heidfeld (Ger) BMW Sauber 1:40:28.388
12 Rubens Barrichello (Bra) Williams 1:40:34.523
13 Adrian Sutil (Ger) Force India 1:40:35.162
14 Kamui Kobayashi (Jpn) BMW Sauber 1:40:36.395
15 Sebastien Buemi (Swi) Scuderia Toro Rosso 1:40:40.015
16 Nico Hulkenberg (Ger) Williams 1:40:41.600
17 Heikki Kovalainen (Fin) Lotus F1 at 1 Laps
18 Lucas di Grassi (Bra) Virgin Racing at 2 Laps
19 Bruno Senna (Bra) HRT-F1 at 2 Laps
20 Christian Klien (Aut) HRT-F1 at 2 Laps
21 Jarno Trulli (Ita) Lotus F1 at 4 Laps

Not Classified:

22 Timo Glock (Ger) Virgin Racing 43 Laps completed
23 Michael Schumacher (Ger) Mercedes GP 0 Laps completed
24 Vitantonio Liuzzi (Ita) Force India 0 Laps completed