The closest aide to Britain's Prince of Wales resigned late Saturday after reports in two newspapers alleging he offered to help secure a British passport and a knighthood for a Saudi businessman.
The Sunday Times and the Mail on Sunday published details of letters to and from Michael Fawcett, chief executive of The Prince's Foundation, in which he expressed the charity's willingness to use its influence on behalf of Mahfouz Marei Mubarak bin Mahfouz.
Mahfouz's family made its fortune in the Middle East through hotels, property and manufacturing.
The newspaper reports said the Saudi businessman's fixers contacted those close to Prince Charles about the prospect of a British honor as early as 2011, and published excerpts from letters between various parties over the subsequent six years.
Donations surpassed £1.5 million
The Sunday Times said Mahfouz had donated more than £1.5 million (€1.75 million, $2.08 million) to royal charities that helped fund renovations of residences used by Charles, and other charitable ventures.
A 2017 letter from Fawcett to one of Mahfouz's aides thanked the businessman for his "ongoing and recent generosity" after he donated cash to help renovate Dumfries House, a Palladian mansion in Scotland, the Mail on Sunday reported.
Fawcett added: "I am happy to confirm to you, in confidence, that we are willing and happy to support and contribute to the application for Citizenship.
"I can further confirm that we are willing to make [an] application to increase His Excellency's honor from Honorary CBE [Commander of the British Empire] to that of KBE [Knight Commander of the British Empire] in accordance with Her Majesty's Honours Committee."
Mahfouz was given a CBE by Prince Charles at Buckingham Palace a year earlier.
The British honors system rewards contributions to arts, sport, sciences, charitable causes and public service but is regularly criticized as the titles still reference to the now-defunct British Empire.
There have been repeated calls to replace the word empire with excellence.
Fawcett resigns 'temporarily'
The charity said in a statement that Fawcett had offered to step aside temporarily so an investigation can be launched.
Mahfouz has denied any wrongdoing. A spokesman for the businessman told the Mail on Sunday he had "not had personal or direct communication to either request, influence or make any arrangements regarding citizenship or knighthood with Mr. Fawcett, or anyone connected to HRH The Prince of Wales or The Prince's Foundation."
The spokesman added that although Mahfouz had expressed interest in applying for citizenship, he decided later not to proceed.
Return of 'cash for honors' scandal
The UK was rocked by a similar cash for honors scandal when it emerged in 2006 that several people nominated for honors had made large loans to the then-ruling Labour Party under Tony Blair.
While the UK has strict rules on even small political donations, a loophole allowed donors to make interest-bearing loans without scrutiny.
Several politicians have also resigned after being linked to scandals involving the payment of cash for asking questions in Parliament.
In another revelation linked to the Prince of Wales, the Mail on Sunday alleged last weekend that a veteran British fundraiser was offering clients dinner with Prince Charles and an overnight stay at Dumfries House in return for a six-figure sum.