Marconi was born to an Irish mother by the name of Annie Jameson. The Jameson family owned a thriving whiskey distillery whose brand is still famous today. Much of their business was based in London, the centre of the British Empire and it was here that Henry Jameson Davis (Marconi's maternal cousin) worked.

Born in 1854, Jameson Davis was over forty and had a great deal of professional experience when in 1896 he welcomed his aunt and young Italian cousin to London. As an engineer he had a consulting office in London that specialized in the planning and construction of cereal mills. It was Jameson Davis who helped Marconi obtain the patent for his invention and introduced him to the Post Office chief engineer, William Preece. He also organized Marconi's first private demonstrations, to which he invited engineers and businessmen.

When Jameson Davis realized the great potential of his cousin's invention, he began to plan its possible commercial development. Rather than simply selling the patent or tying into an agreement with the Post Office he proposed to Marconi that they found a company together. Davis managed to raise financial backing from various business associates, many of whom were grain merchants.

Marconi hesitated for some months, but finally agreed to his cousin's idea and on 20 July 1897 the Wireless Telegraph and Signal Company was founded. In 1900 its name was changed to the Marconi's Wireless Telegraph Company. The company's capital accounted for 100,000 stock options, each worth £1. Marconi was appointed technical director and Jameson Davis financial director.

For almost a year and a half Henry Jameson Davis was the key driving figure, legal advisor and reference point, without whom Marconi could not have found his way in the City. For several years the two cousins got along amicably sharing the many organisational and financial difficulties experienced by the company before it became well-established. Over the years Jameson Davis' role within the company lost some of its importance and in 1912 he decided to sell his shares and leave.

He died in 1936, just one year before his famous cousin.

Regardless of their disagreements and misunderstandings, it is easy to imagine the emotion Henry Jameson Davis felt, when in 1909 Marconi was awarded the Nobel Prize for Physics in Stockholm. Davis had reason to be proud, both as a relative and as a businessman, for he too had greatly contributed to the success of the business enterprise.