Chelsea Football Club owner Roman Abramovich told a High Court judge that he "never aspired to be a 'public figure"'.
Mr Abramovich accepted that he had a "high media profile" but said he had "always been interested primarily in real business".
The 45-year-old Russian billionaire businessman is being sued for billions of pounds by exiled Russian oligarch Boris Berezovsky, 65, in a trial before Mrs Justice Gloster at the Commercial Court in London.
Mr Berezovsky says Mr Abramovich "betrayed" him and "intimidated" him into selling shares in Russian oil company Sibneft for a "mere $1.3 billion" (£800 million) - "a fraction of their true worth".
He alleges breach of trust and breach of contract and is claiming more than £3 billion in damages.
Mr Abramovich denies the allegations and denies that Mr Berezovsky is entitled to damages. He says Mr Berezovsky was paid millions of pounds for his services as a "political godfather" but was not a business partner.
The court has heard that Mr Berezovsky "fled Russia, never to return" in late 2000, following a fall-out with then president Vladimir Putin - travelling initially to France then settling in England.
Mr Abramovich was today giving evidence for a second day - and is expected to be in the witness box for the rest of the week.
The trial began early in October.
"Although I now have a high media profile, I never aspired to be a public figure," said Mr Abramovich in a written witness statement given to the judge.
"I have always been interested primarily in real business and the development of business strategies."
In his witness statement, Mr Abramovich outlines his business career in a three-page section - but makes no mention of Chelsea.
He refers to his "acquisition" of the club, in 2003, in a section headed "political and charitable" activities.
But today Mr Abramovich told the court that his purchase of Chelsea "impacted" his way of life "significantly".
"I think that when I bought Chelsea Football Club, that did impact my way of life significantly," he said. "It was a turning point really."
Mr Abramovich says, in the statement, that he met Mr Berezovsky in 1994, was "surprised" by the oligarch's "extravagant lifestyle" and was never interested in "imitating" that lifestyle.
Laurence Rabinowitz QC, for Mr Berezovsky, today questioned Mr Abramovich about that "assertion" .
"You say here that when you met Mr Berezovsky you were 'quite surprised' at his 'extravagant lifestyle' and that you personally were 'never interested in imitating this lifestyle',", said Mr Rabinowitz.
"Can we just consider the truthfulness of this assertion, Mr Abramovich, that you, unlike Mr Berezovsky, have never had an interest in what you label an extravagant lifestyle."
Mr Rabinowitz listed some of the properties Mr Abramovich had owned including: "Fyning Hill, a 420-acre estate and house in West Sussex"; "Lowndes Square, a large and expensive central London property near Knightsbridge" and a "multi-million pound" French chateau "which once belonged to the Duke and Duchess of Windsor".
He added: "You say you were 'never interested in imitating this lifestyle'. But you now want to qualify that, do you, to say whilst you weren't interested in a lifestyle then, you may have an extravagant lifestyle now?"
Mr Abramovich replied: "Well, yes, possibly. I agree, yes, that one could put it that way. But at that time this was not part of my position."
Mr Rabinowitz asked: "So when did this change, Mr Abramovich?"
Mr Abramovich said the change came when he bought Chelsea.