Boris Johnson’s close friend Jennifer Arcuri was invited to a Buckingham Palace reception hosted by the Duke of York.
She told pals she expected further investment in her business after the 2014 event.
But it is unclear how she secured the ticket to the D5 Summit of “digital governments”.
Her Innotech Network was not among nine British companies formally invited, according to an answer to a Commons question.
Ms Arcuri’s firm received £11,500 sponsorship from the mayor’s promotional agency during Mr Johnson’s time as Mayor of London.
He has promised to co-operate with a possible conflict of interest probe and denied he had anything to do with the sponsorship.
Ms Arcuri, 34, was invited to three overseas trips with Mr Johnson in the space of a year, he spoke several times at her Innotech summits and is said to have been a regular visitor to her East London penthouse.
A separate investigation has been launched into how another Arcuri firm, Hacker House, secured £100,000 in 2018 from the Department for Culture, Media and Sport.
It is understood the firm, now run from California by Arcuri and her British husband, was eligible for the training grant because it had a UK phone number although that number now connects to a US call centre.
Accounts show it had just £84,972 in assets at the end of the last financial year but owed £713,354 to Ms Arcuri for an “interest-free loan” to her own company.
In April 2016 Hacker House called for young hackers and coders to help the firm develop a set of “cyber skill badges as requested and prepared for the Duke of York”.
The Mirror understands this relates to Andrew’s iDEA badges, a scheme focusing on digital literacy.
Ms Arcuri did not respond to a request for comment on her Palace trip but has said any grants or trade missions reflect her role as a businesswoman.
Buckingham Palace and No10 would not comment on the invitation.
