Engineers at the National Motor Museum in Beaulieu have initiated the extensive cleaning and restoration efforts of a three-speed gearbox from the Sunbeam 1000hp, a British car that broke the 200mph Land Speed Record nearly a century ago.

Unique in its construction, it was designed to operate the rear wheels, as Sunbeam's designer, Captain Jack Irving, had concerns about transmitting such substantial power through a standard rear axle.

The novel use of drive chains, which became red-hot during the initial tests at Wolverhampton, showcased this remarkable technical innovation.

The intricate restoration process involves a three-part assembly comprising of the three-speed gearbox, bevel drive, and spur gearbox - housed within the vast Sunbeam chassis and neighbouring its Land Speed Record driver, Sir Henry Segrave.

National Motor Museum senior engineer Ian Stanfield said: "The learning curve has been in taking units apart. Once that’s been completed, we know how to put them back together again.

"We are where we want to be at this stage of the restoration process and are looking forward to the next challenge of reassembling the rear engine. We are also working on the air starter mechanism, another part of the process which has been complicated by needing to manufacture replacements for so many parts which are missing."

The engineers have had to devise innovative methods to carefully disassemble and clean this historical artefact.

Significant steps include handcrafting new parts, such as a sealant gasket, for the gearbox and bevel drive.

As for the spur gearbox, the last component of the transmission system, it had to be soaked for a week in a hot water and detergent solution to dissolve the hardened oil, before further cleaning and restoration could take place.

The restored assemblies will then be reinstalled into the revitalised chassis.

As it stands, visitors can view the stripped-down chassis at the National Motor Museum during their trip to Beaulieu.

The Sunbeam 1000hp Restoration Campaign, launched in collaboration with Hampshire-based Brookspeed Automotive, seeks to raise £300,000 to complete 'The Slug's' refurbishment.

The plan is to debut the fully restored car on Daytona Beach in Florida in 2027, marking the 100th anniversary of its record-breaking run.

However, the vehicle's two 22.5-litre engines, capable of yielding 435bhp each, have remained dormant for over 80 years due to internal corrosion.

It remains the engineers' objective to revive the auditory and olfactory experiences of the fastest car of its time and ensure its preservation for future generations.