When a story broke over the weekend about Boris Johnson’s friendship with an American tech entrepreneur who was granted £126,000 in public money during his time as London mayor, the entrepreneur in question had little to say.

Jennifer Arcuri, suddenly at the centre of a row over an alleged conflict of interest, did not address questions about the friendship, simply insisting that the grants received by her companies were entirely justified and “purely in respect of my role as a legitimate businesswoman”.

Back in Johnson’s mayoral years, though, Arcuri was fond of boasting about the pair’s strong personal connection. She would show tech industry colleagues messages from the mayor on her union jack-clad phone, one of her contacts said, and stored his number under the name “Alex the Great”.

“It stuck in my mind because I was slow to twig that it referred to Boris’s real first name,” the source said. “It was very clear from the messages that this was closer than a business friendship. She also talked about Johnson’s visit to her flat in Shoreditch. It looked like hubris.”

As the dust settles from the explosive story, Johnson is under mounting pressure to explain how public money and favours were granted to Arcuri and Innotech during his time as London mayor. And more details are emerging of the nature of the relationship between the two.

The strength of their friendship appeared to be confirmed by Johnson’s willingness to speak for free at events organised by Arcuri’s company Innotech. At these events Arcuri went out of her way to make Johnson feel welcome. At one Innotech summit in 2013 she had a cake baked in the shape of London’s City Hall and Canary Wharf, which included three icing sugar figurines of Johnson and his trademark blond hair. She then posed for a photo while eating a cake decoration shaped like the mayor.

Jennifer Arcuri with Boris Johnson in 2013. Photograph: Vicki Couchman/Rex/Shutterstock

At another Innotech event a year later she put on an elaborate tea ceremony as a backdrop for Johnson to announce a fund for Middle East startups. “I’m always happy to hang out at Innotech,” Johnson told Arcuri before she poured him a cup of tea and thanked him profusely.

She had reason to be grateful. In October 2013 the mayor’s promotional agency London & Partners (L&P) granted Arcuri’s company £10,000 in sponsorship. Another £1,500 was to follow.

An L&P spokesman said: “The money which we gave to her company was not a grant but a commercial sponsorship. The mayor wasn’t involved in the decision.”

Johnson’s register of interests as mayor makes no mention of Arcuri or Innotech. And he has repeatedly refused to answer questions about Arcuri since revelations about their relationship first appeared in the Sunday Times.

But Arcuri has left an online trail that makes much of her connection to Johnson. Her self-written biography on the film database IMDb mentions that her company “captured the attention of the London Mayor, Boris Johnson” and that he gave its first ever keynote speech.

Her credits on IMDb include the role of a girl on a London street in the Bollywood comedy Naughty @ Forty, described as the story of how a “male virgin with sleep-walking problems finds true love after getting married to a naive child-like woman”. She is also listed as playing Mae West in the Wright Stuff, a TV series that spoofed early black and white films.

She had made her way to London to study for a MBA, and joined Johnson’s successful mayoral re-election campaign in 2012. In March 2013, after Johnson faced a famously tough interview with Eddie Mair on the BBC about his conduct, including claims he made up quotes as a journalist and lied about an extra-marital affair, Arcuri leapt to his defence on Twitter.

She said Johnson’s personal business was not for the public to judge.

In response to a Twitter user who said Johnson looked like a “bumbling fool”, she wrote: “Yesterday was a hiccup. It happens. Did every1 forget all the good he has done for #london?”

Yesterday was a hiccup. It happens. Did every1 forget all the good he has done for #london? @MayorofLondon @lozmoore_ — Jennifer Arcuri (@Jennifer_Arcuri) March 25, 2013

Arcuri was initially denied access to two trade trips organised by L&P to New York and Israel. But after intervention from Johnson’s office, she was allowed to join them.

The L&P spokesman said: “On the trade missions she was declined on two of them, and then at the request of Boris’s team was given varying degrees of access to both New York and Tel Aviv. For a third trip to Malaysia and Singapore she applied and was accepted, and again Boris was not involved in that decision.”

Asked if a declaration of interest had been declared, he said: “Not that I can see.”

One tech chief executive, who attended a five-day visit to Israel with Johnson and Arcuri in late 2015, said she was “out of place on the trip”.

The CEO, who did not wish to be named, said Johnson had questions to answer. “If she was there because she was his friend, that seems completely unfair,” he said. “There’s always great tech that should be out being promoted. If she’s there because of Boris’ personal interest with her that’s appalling.”

Another, Aldo de Pape, founder and chief executive of TeachPitch, a web-based learning platform that helps teachers and schools identify the best online resources available, said Arcuri told fellow delegates she was friends with Johnson.

De Pape said: “She was quite vocal and fairly eccentric in how she expressed herself and also quite open about her personal relationship with Johnson. She said she was friends with him. She didn’t imply anything romantic.”

He said Johnson should explain his relationship with Arcuri. He said: “If she has been given public money just because of her personal relationship with Johnson then he should answer to that because that should not be the way to go. What’s the deal?”

Andrew Dismore, a Labour London assembly member who was on the finance committee at the end of Johnson’s mayoralty, said: “Boris has got a lot of explaining to do. It looks like he was using the GLA as his private fiefdom for his friends.”

He also threatened to summons documents from L&P about how it made grants to Arcuri and how she was given a place on trade missions.

Dismore said: “We have been having a long-running battle with L&P about their lack of transparency. They operate in a very secretive way. We’ll see what comes out of them voluntarily first. But if we have to summons the paperwork them I’m sure we will. We need to be satisfied that due process was followed in the way this money was awarded.”

A spokesman for the current London mayor, Sadiq Khan, stressed that the trade missions were a matter for Johnson. But Khan has asked his officials to “look into what processes were followed during that time and that lessons are learnt for the future”.