Lewis Hamilton on Sunday paid tribute to the late Niki Lauda after wrapping up his sixth world title, claiming the Mercedes team mentor was with him “in spirit.”

Triple world champion Lauda passed away in May at the age of 70 and the Austrian legend was very much in the mind of 34-year-old Hamilton after he secured this season’s title.

“I miss him so much and I know he would take his cap off here today,” Hamilton said. “I am sure he is here in spirit.”

Hamilton said that he felt this season had been his hardest year to date in fighting to win the championship.

“Behind the scenes, we have worked so hard and it is so challenging to us all, and every message of support is important from everyone, so much that people don’t believe,” he said after finishing second at the US Grand Prix to teammate Valtteri Bottas. “That is why I try to put out messages that are positive. We all struggle and if it helps just one person then it is worth it.”

“It’s overwhelming if I’m honest. It was a tough race today and yesterday was a difficult day for us,” he said earlier. “I didn’t know if it would be possible, but I worked as hard as I could here and with my team back at the factory.”

Speaking in the dramatic aftermath of the race, Hamilton expressed his feelings quietly and paid tribute to his father Anthony and the rest of his family.

“Right now, honestly, it is hard to understand what I have done today, but I feel very happy,” Hamilton said. “It is just pure, pure happiness. I am happier than ever, but this has been harder than ever. Just now, I saw my parents, my family, as I came in and I saw my dad’s smile, and that means it all to me.”

“My mum, my dad, step mum and step dad, and all my family are here, and it’s an honor to be here [with six titles] with those greats,” said Hamilton, who is one title ahead of Juan Manuel Fangio and just one behind the all-time record of seven held by Michael Schumacher. “My dad told me, when I was like six or seven, never to give up and that’s kind of the family motto.”

Asked how many more titles he can win, he said: “I don’t know about championships, but as an athlete I feel as fresh as I can be and these next races we will keep pushing.”