MEXICO CITY • Lewis Hamilton was left still trying to take on board the magnitude of his achievement of becoming a five-time Formula One world champion after he secured the title at the Mexican Grand Prix on Sunday.

The Briton said that he had performed at his very best all year in the face of stiff opposition from Ferrari's Sebastian Vettel, while the German admitted he had just not been good enough.

After his fourth-placed finish ensured he retained the championship, the 33-year-old conceded the enormity of his achievement had yet to sink in.

"It is hard to realise it at the moment," Hamilton, who was congratulated by Hollywood actor Will Smith over the radio, said.

"I dreamt of it, but I never thought in a million years that I would be standing here as a five-time world champion."

The 33-year-old, who equalled the late Argentinian great Juan Manuel Fangio's feat, felt that his 12th season in Formula One had been his "best yet" after becoming more self-critical.

"I asked, 'How can I improve?'" he said. "To do that, you have to get the car in the right place, and you've got to work with the team to help unleash what's great and unleash the greatness in yourself."

Hamilton also told BBC Sport that his Mexico win came against the backdrop of the death of his grandfather Davidson four days earlier.

Paying tribute to him and his father Anthony, he said: "Our grandfather would be so proud of us, and grateful the Hamilton name is there, established and will go down now in history."

The journey to his fourth title in five years first started in the post-season in 2016, when he had lost out on the championship to then Mercedes teammate Nico Rosberg amid tensions in the team.

Mercedes executive director Toto Wolff invited him to his Oxford home and the clear-the-air talks opened "the door to a new room", with Hamilton now driving at a level that none of his peers can match.

German great Michael Schumacher's record of seven titles is within his reach but, at the moment, the ace is just "very humbled" to be the joint-second most decorated F1 driver of all time.

"Let me just try and realise that I've won this one," Hamilton commented when asked about whether he could surpass Schumacher, who has also won 20 more races than the Briton's 71.

Despite a first double podium success in Mexico in 28 years for Ferrari, Vettel, who finished runner-up to Red Bull's Max Verstappen and ahead of teammate Kimi Raikkonen, could only look back on the errors this season that cost the Italian team a tilt at the drivers' title.

His biggest blunder occurred when he crashed into a tyre wall at Hockenheim while in first place, and three similar incidents following the German Grand Prix - in Italy, Japan and Texas - gave Hamilton an unassailable lead.

"I have now had three times that disappointment in one day where you realise you can't win the championship," said the 31-year-old, who acknowledged that the team had not made the best of what, at times, was the best car in the field. "We had our chances but in the end, we weren't good enough."

Vettel, however, was among the first of Hamilton's contemporaries to recognise his achievement.

"He drove superbly all year and he was better all year. No. 5 is incredible. I asked him to keep pushing for next year. I need him at his best to fight him again," the German told reporters.

Four-time world champion Alain Prost also praised Hamilton, saying: "He is the best or, one of the best, of this generation. It was impossible to beat him this year."

While the title is wrapped up, there is still the matter of the constructors' championship, with Mercedes enjoying a 55-point lead over Ferrari on 585 points with two races left on the calendar.

And, in classic Hamilton fashion, he wants to cap his best year by winning in Brazil on Nov 11, which would be the best way for him to show appreciation for his team's "amazing support".

AGENCE FRANCE-PRESSE, REUTERS, THE TIMES, LONDON, THE GUARDIAN