Chelsea owner Roman Abramovich will not be able to work in the UK if he arrives on an Israeli passport, a Downing Street spokesman has said.
Abramovich flew to Israel on Monday after receiving confirmation that he was eligible for citizenship under the country's Law of Return, which allows Jews to become citizens.
Israeli passport holders are permitted to enter the UK without a visa for short stays, although it is unclear whether this was the primary motive for Abramovich's decision.
Abramovich has experienced a delay in renewing the Tier 1 investor visa he has used to visit London in recent years, with the issue meaning that he missed Chelsea's FA Cup final victory over Manchester United earlier this month.
Sources said the UK authorities were demanding that he declared the source of his fortune before a new visa was issued.
While Abramovich will be able to enter the UK on an Israeli passport, he still requires a visa if he wishes to work.
"Those with Israeli passports are non-visa nationals, which means they do not need a visa to come to the UK as a visitor for a maximum period of six months," a spokesman for UK Prime Minister Theresa May told the Guardian.
"Israelis are required to obtain a visa if they want to live, work or study in the UK."
The spokesman added that the Home Office would judge what constitutes work.
Abramovich owns Chelsea, but the day-to-day running of the football side of the club is overseen by director Marina Granovskaia.