The only other man who could have prevented Hamilton tying things up in Austin - Ferrari’s Sebastian Vettel - took third place in a race which featured two virtual and two actual safety-car periods, and one in which the eventual outcome was never anything but impossible to predict.
"That’s the greatest moment of my life," was how Hamilton summed up his emotions over team radio after taking the chequered flag for this tenth win of the season and the 43rd of his career, becoming only the second Briton after Sir Jackie Stewart to become a three-time world champion.
As the weather gods finally smiled on the Circuit of The Americas, for a long time it looked like Mercedes’ one-two in a crash-strewn race was going to be the wrong way round, with Rosberg seemingly headed for victory. Hamilton needed to be in front of the German in order to ensure that he outscored Vettel by nine points.
Rosberg had lost the lead as Hamilton aggressively eased him aside in the first corner, but retaken it from Red Bull’s Daniel Ricciardo during the pit stops on the 19th lap and held it through various virtual and real safety car interventions until the 48th lap.
Then, under pressure from Hamilton, he slid wide in Turn 12, and suddenly the roles were crucially reversed. Hamilton, who had clearly struggled initially on intermediate tyres on a very slippery track, was thus able to take not only to his 10th win of the year, but the one that would allow him to realise his life ambition of matching his hero Ayrton Senna’s three championships.
It nearly didn’t happen in Texas, however. Vettel had driven brilliantly to climb from 13th on the grid to seventh in a rough opening lap, and was set to run to the finish on a set of medium Pirelli slicks after his pit stop, until the safety cars foiled that gamble. On fresh soft tyres he was hounding Rosberg in the closing laps, and had he overtaken him, Hamilton would have had to wait longer for his new crown. But a deeply disappointed Rosberg held on, by half a second.
Fourth place fell to Max Verstappen, who drove his usual feisty race as Toro Rosso gambled like Vettel, but without the final stop for fresh rubber. The Dutchman was comfortably clear of a fabulous fight between Force India’s Sergio Perez, Toro Rosso’s Carlos Sainz and the McLarens.
Fernando Alonso fell away towards the end, losing out to Ricciardo for P10 on the final lap, but when Sainz had a five-second time penalty added for pit-lane speeding, he dropped behind Jenson Button, who chased the Spaniard and the Mexican home on the road.
Pastor Maldonado was eighth for Lotus, having at one stage eased Button off the road, and Felipe Nasr salvaged two points for Sauber in a forgettable 400th Grand Prix for the Swiss team which saw him collide with team mate Marcus Ericsson on the opening lap. The Swede later triggered a safety car intervention when his car stopped on track with a loss of power.
It turned out to be an awful afternoon for Red Bull, too. Ricciardo was very racy in the slippery early going and overtook Rosberg, team mate Daniil Kvyat and Hamilton to lead easily from the 15th to the 19th lap, but he lost his edge when the road dried enough for slicks from the 19th lap onwards. He was attacked by Force India’s Nico Hulkenberg on the 36th lap, with the German slamming into the side of his car and eliminating himself, as well as causing damage to the Red Bull. The stewards investigated the collision after the race, but decided to take no further action against Hulkenberg on the basis that his front wing had become dislodged under braking and impaired his ability to brake effectively for the corner.
Ricciardo was later passed by Sainz, and a resultant pit stop dropped him to 12th. Kvyat, meanwhile, spun his car heavily into the wall heading down to Turn 20 on the 42nd lap, triggering the final safety car which proved so timely to Hamilton.It was also a day when Marussia looked a points contender due to the high rate of attrition. Alexander Rossi took 12th in his home race, as team mate Will Stevens joined a retirements list which comprised eight cars.
Kimi Raikkonen was forced out with overheating brakes, damaged after he hit the wall at Turn 7 early on. The Finn had pitted for a new nose and rejoined the race, before his car cried enough. Felipe Massa and Valtteri Bottas were both forced out with technical issues - Williams’ first double DNF since Brazil 2012 - while Lotus’s Romain Grosjean completed the non-finishers.
Hamilton thus came away with an unassailable points total of 327 - with Vettel on 251 and Rosberg 247 - with three rounds of the season remaining.