When Johnson was six months old, his mother fatally stabbed his father after an argument over a burnt meal; although two guests attempted to assist him, Patrick Johnson died two days later aged thirty one.[8] Johnson's mother, aged twenty seven, was found guilty of manslaughter on grounds of diminished responsibility, and sent to Rooksdown Hospital in Hampshire; she was subsequently released and later remarried to Dr Ivan Brumpt.[8] Johnson and his older sister were raised by their maternal grandparents.[8]
Johnson began his career in finance with Robert Fleming & Co. in 1995, and then with Jardine Fleming, Hong Kong, in 1998.[10] In 2001, he went into asset management, and worked for Lloyd George Management until 2007.[10][11] In 2007, he co-founded Somerset Capital Management (SCM) with Sir Jacob Rees-Mogg and Edward Robertson.[10][12] All three were colleagues at Lloyd George Management in Hong Kong.[13] Rees-Mogg was CEO of SCM until Johnson succeeded him in 2010.[13]
In September 2022, SCM with assets under management of about $5 billion was up for sale, with Johnson planning to move into politics, and would be succeeded by chief operating officer Robert Diggle as CEO.[14]
In 2016, when his friend David Cameron stood down as Prime Minister, Johnson gave him the use of his £2,650-a-week Chelsea house,[2] and Cameron accordingly declared a benefit of more than £37,000 in the register of MPs' interests.[15]
In 2024 it was reported that Johnson “made clear that he was keen to see a bigger Infosys presence in the UK and would be happy to do what he could to facilitate that”.[19]
^Debrett's Peerage & Baronetage : comprising information concerning the Royal Family, the Peerage and Baronetage (147th ed.). Debrett's. 2012. p. 638. ISBN9781870520805.