[2] He was educated at Cambridge University, where his interests in motor racing first developed as a mechanic to his elder brother Sir Algernon Guinness.

As for many racing motorists of this era, Guinness had commercial interests in automotive engineering; in this case being the inventor of the KLG spark plug, a brand name surviving today.

In 1912 Guinness acquired the disused 'Bald Faced Stag' inn at Putney Vale, where production of these plugs began in a small way, supplying other racers including Segrave and Malcolm Campbell.

[3] As the war continued, KLG plugs developed a reputation for reliability in aircraft use, leading to a large increase in demand.

[6] In 1920 Guinness was made a member of the Order of the British Empire for his services as manager of the Robinhood Works.

[5][3] KLG's reliability was particularly attractive to the land speed record contenders and their many-cylindered aero-engines, often with dual ignition systems.

Segrave's 1,000HP Sunbeam required 48 spark plugs, a mis-fire amongst which could be very difficult to detect and replace on a windswept beach.

The car was later sold to Malcolm Campbell, who named it "Blue Bird" and also used it to set land speed records.

In 1926, after Guinness's retirement from motor racing, he and his friend Malcolm Campbell used the yacht for a treasure-hunting trip to the Cocos Islands.

[1] At the coroner's inquest, his brother Sir Algernon Guinness produced a letter that indicated the likelihood of suicide.