Moments after he recaptured the lead of the world championship from Mercedes team-mate Valtteri Bottas following his fine victory at the Circuit de Catalunya, Hamilton dedicated the triumph to Harry Shaw, a five-year-old who has been diagnosed with a rare form of bone cancer.
Other non-F1 drivers taking part in Tuesday's test included Pietro Fittipaldi - the grandson of two-time champion Emerson - in the Haas, Blancpain GT driver Nick Yelloly in the Racing Point and F2 championship leader Nicholas Latifi in the Williams.
But while his antics cost him pace in the opening stint, it also cost Bottas as instead of challenging Hamilton, he had to fend off Vettel while both did their best to avoid a collision.
The rumours began to circulate when Mercedes boss Toto Wolff suggested that Hamilton might look to finish his career with the legendary Italian team.
"It's incredible what we're achieving and what we have achieved in these six and a half years". I'm very proud of everyone back at the factory and thankful for all their hard work. "That is my sole goal and my sole objective".
The Finn's first lap in Q3 was blistering, his 1m 15.406s more than half a second quicker than anyone else - but Hamilton, who was his closest challenger, had made a mistake at turn eight, leaving time on the table.
The race start saw a three-way battle between pole-sitter Bottas, Hamilton and Sebastian Vettel.
Verstappen took advantage of the joisting to slip by Vettel and into third. Vettel let his teammate Charles Leclerc through to 4th place on Lap 12, but by then Leclerc was already 11sec off the lead.
Bottas had shown faster speed in practice and in qualifying than Hamilton, when Bottas set a scorching track record that was a whopping 0.6 seconds faster than the Brit's best effort.
But Bottas' chances for victory were sunk by his poor start, when his wheels appeared to spin while Hamilton immediately made up the difference.
"It was pretty tight but I lost it at the start, there was some odd behaviour on the clutch - it was like biting, releasing, biting, releasing and I've not felt that before", said Bottas. "I feft some unusual behavior with the clutch".
"It is really annoying".
"If we have a strong weekend from Ferrari in Monaco, everybody will say "this stopped Mercedes, at least it's the end of the Mercedes dominance of this year".
The Austrian, who has been talked of as a possible replacement for Formula One chairman Chase Carey post-2020, acknowledged there was a lot of talk but said he was relishing his role at Mercedes.
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