Lewis Hamilton bade a final goodbye to staff at McLaren's headquarters on Friday ahead of his move to Mercedes next season.
Hamilton joined the Woking team at the tender age of 13 in 1998. However, his association with them comes to an end on December 31.
"It was the hardest decision I've ever made," Hamilton is quoted as saying by the Daily Mail.
He added: "It is to do with the process of growing up, of leaving home. That's why I am taking the next step, to grow as a driver and as a human being."
According to reports, the 27-year-old's farewell to those who helped him win the World Championship in 2008 was "warm and friendly".
"My time at McLaren has been fantastic," Hamilton told staff at the McLaren Technology Centre.
"When I arrived in Formula 1 in 2007, I now realise I never really grasped what I was taking on. Ron [Dennis] had told me: 'Don't be surprised if you're 0.5sec slower than Fernando [Alonso]', and I just smiled because I knew it wouldn't be the case. But, even so, that year was very hard, for many reasons.
"The following year, 2008, as a result of so much hard work from all of you, we won the Championship. Thanks so much. You were brilliant - you still are. I have so much affection and love for this team. And that's why McLaren has always felt like home."
He received a three-foot model of his 2008 Championship winning car and he emotionally ended off saying: "Maybe I'll come back one day...if you'll have me."
Hamilton had his final outing as a McLaren driver in Malta on Sunday as part of an event organised by team sponsor Vodafone.
Speaking to Sky Sports News, Hamilton said he was targeting podium finishes in 2013, adding that Mercedes could reach the top step if things go "really, really well".
However, Hamilton added that the 2014 season - when major rule changes are introduced - represents Mercedes' best hope of mounting a title challenge.
"I think the guys have great, great potential and that's why I'm going there," he said.
"I don't see it as a short-term thing. For me personally, I don't get in the car until February, so I won't be able to have a big enough impact until at least six months down the line.
"I think 2014 has to be the most important year, or the most competitive year. But I don't see why we can't try and clinch a few podiums.
"If we get some wins next year - if it just happens to go really, really well - then we'll be smiling. But we'll see."