The car in question is the MP-4 21, one of the first F1 cars to be tested by a then-21-year-old Hamilton.
The MP-4 21 was the creation of car designer extraordinaire Adrian Newey in his final year with McLaren.
After being tested by Hamilton, the MP-4 21 was driven by Juan Pablo Montoya in the first three grands prix of the 2006 F1 season.
After being tested by Hamilton, the MP-4 21 was driven by Juan Pablo Montoya in the first three grands prix of the 2006 F1 season.
The MP-4 21 was the first McLaren powered by a Mercedes-Benz FO108S 2.4-liter naturally aspirated V-8 engine.
This particular car, chassis 21A-03, has been restored to functional specification and retains its original engine, gearbox, onboard computer, and steering wheel.
The rarity of this auctioned car is that it isn't often a Hamilton-driven F1 car exists outside of a factory collection.
A year later, in 2007, Hamilton would claim his first F1 championship. This MP-4 21 played a small part in his historic feat, as an early test car for the legendary driver.
The MP-4 21 was auctioned by Sotheby's on Friday with a guide price of £2.2m-£2.7m, according to Top Gear.
The auction began days ago, meaning somebody out there - someone with a spare seven-figure sum - will soon be the proud new owner of the McLaren MP-4 21.