Hampshire played a pivotal role in the liberation of Europe during the Second World War, extending far beyond the initial D-Day landings. After the invasion, the focus shifted to supplying the Allied forces in Normandy with the necessary materials for the prolonged Battle of Normandy. This effort included Operation Pluto, which was crucial for transporting fuel across the English Channel.

Before D-Day, the British War Office estimated more than 60 per cent of the supplies needed by the Allied forces would be petrol, oil, and lubricants. Initially, fuel was supplied in jerricans and drums, transported by sea and lorry. However, because of high demand for shipping and the lack of a suitable French port, an innovative plan was devised to lay pipelines across the Channel.

In April 1942, Vice-Admiral Lord Louis Mountbatten proposed the idea of an oil pipeline to the Secretary for Petroleum, Geoffrey Lloyd. While pipelines were common in ports and short distances, laying one across the Channel was unprecedented. Despite the challenges, the success of a high-pressure pipeline in Iran encouraged the Petroleum Warfare Department to proceed with the Channel pipeline, which would be armoured to withstand high pressures and deployed by specially-modified cable-layer ships.

The project, codenamed Pluto (Pipeline Under the Ocean), involved developing two types of pipelines: Hais, made from extruded lead, and Hamel, made from mild steel. Trials were successful, and pumping stations were established at Sandown on the Isle of Wight and Dungeness on the Kent coast.

Construction was carried out at night and in secret, and equipment was carried under tarpaulins. The pumping stations and storage tanks were camouflaged to look like villas, seaside cottages, old forts, amusement parks and other innocuous features. The locations were erased from maps. Lorry drivers conducting deliveries had to phone from a public phone booth for instructions.

Sandown was connected to the Avonmouth-Thames pipeline system through a link to Fawley Refinery on the Hampshire coast, with the pipeline completed by March 1944. A branch line was also constructed from Dungeness to Walton-on-Thames. In France, Sandown was to connect to Cherbourg, and Dungeness to Ambleteuse, with the codenames 'Bambi' and 'Dumbo' respectively.

According to the Operation Overlord plan, Cherbourg was expected to be captured within eight days of D-Day. However, because of German resistance, the capture was delayed, and Cherbourg didn’t fall to the Allies until June 27, 1944. Despite initial pipeline failures, successful installations eventually occurred. On September 22, a Hais cable delivered 56,000 gallons per day, followed by a Hamel cable on September 29.

Unfortunately, both pipelines failed on October 3 due to technical issues, and Operation Bambi was terminated. But using the lessons of the Hampshire pipeline, Operation Dumbo, connecting Dungeness to Boulogne, achieved more success. A Hais pipeline began pumping on October 26, and by December, multiple pipelines were in operation, delivering significant amounts of fuel to the European mainline. Despite challenges, the Dumbo lines continued to function, eventually extending to Calais and connecting to an inland pipeline system reaching Antwerp, Eindhoven, and Emmerich.

By March 1945, Dumbo was delivering over a million gallons per day, surpassing its target, and by April, it was providing 4,500 long tons of fuel daily to the Rhine. The operation continued until August 1945, by which time it had transported 180 million gallons of petrol. Operation Pluto was officially disbanded on August 31, 1945, having significantly contributed to the Allied war effort by delivering 370,000 long tons of petroleum products.

Winston Churchill lauded Operation Pluto as "a wholly British achievement and a piece of amphibious engineering skill of which we may well be proud". After the war, most of the pipeline was salvaged and scrapped, but many of the buildings used in the operation, particularly on the Isle of Wight, remain. The derelict Palmerston forts housed 13 of the 16 Sandown pumps, with the five remaining ones at what are now Brown's family golf course and the Grand Hotel.