Jennifer Arcuri joining Boris Johnson on his mayoral campaign in 2012. Her firm received cash from an agency for which he was responsible

Boris Johnson failed to declare a series of potential conflicts of interest over a close friendship with an American model turned technology entrepreneur during his time as London mayor.

An investigation by The Sunday Times can reveal that the woman, Jennifer Arcuri, was given a total of £126,000 in public money and privileged access to three official overseas trade missions led by Johnson.

Sources have confirmed that Johnson, now 55 and prime minister, was a regular visitor to Arcuri’s top-floor flat in Shoreditch, east London.

Arcuri, who was in her late twenties at the time, is claimed to have described him as “one of her best friends”.

Evidence obtained by this newspaper shows that in 2013 Arcuri’s fledgling business received £10,000 in sponsorship cash from