Jennifer Arcuri has revealed she had a 'codename' for Boris Johnson that was designed to mask their friendship when he rang on the phone.
The tech entrepreneur saved the top Tory as "Alexander the Great" after the Ancient Greek military leader - and his first name, Alex.
It came as she - but denied he offered her "favours" while London mayor.
She told ITV's Good Morning Britain they exchanged numbers after she met him during public events - and "immediately bonded over a mutual love of classic literature".
"He said no no no, my team will throw [your card] away, I just want to be able to contact you directly," she said. "So I said well, you can call me. So I gave him my number and that was that.
"The first message I was out with my friends and it came in - 'Boris calling Jennifer'.
"And my friends were like 'you can't have his number, you can't have his name, you know like that, you have to guard his privacy'.
"And I was like 'oh okay' and they said 'put it under a codename' and I was like 'oh alright, what codename?' and they were like 'call him Alexander the Great!'
"So I put it in as Alex the Great and that's how he stayed."
Tech guru and former model Ms Arcuri exploded into headlines last month after it emerged she was given access to three foreign trade trips and had Mr Johnson speak at four of her events when he was London mayor.
Mr Johnson to a conflict-of-interests probe in the London Assembly - whose rules forbid favourable treatment to friends.
And the Prime Minister, who has claimed there was "no interest to declare", has also been referred to the police complaints body to assess whether he should face a criminal investigation.
Despite the top-level access - which began after they met in October 2011 - Ms Arcuri today insisted "Boris never ever gave me favouritism".
But she repeatedly refused to deny claims by acquaintances that she had a sexual relationship with the 55-year-old PM.
She also refused to say how many times Mr Johnson visited her Shoreditch flat, which contained an office and a pole-dancing pole. And
Shadow Chancellor John McDonnell today accused Boris Johnson of misleading the public and branded him "unfit for office" in the wake of the interview.
He said: “As Mayor, Boris Johnson had a duty under the Greater London Authority code of conduct to declare his friendship with Jennifer Arcuri and not to act in a way that benefited her business.
“Regardless of the exact nature of his relationship with Arcuri, it is clear that she and Boris Johnson were close, and that he misled the public when he said “there was no interest to declare”.
“The Prime Minister is unfit for office. This morning has thrown up even more questions for Boris Johnson, which can only be answered with a full investigation into the apparent misuse of public funds.”
