Prince Charles has made it clear that he had "no knowledge" that his closest aide was helping a Saudi billionaire secure a knighthood and British citizenship.

Michael Fawcett, who has been in the royal's service for several decades and handles his numerous charitable initiatives, recently resigned from his position after reports in the Sunday Times and Mail on Sunday claimed that he was involved in a "cash-for-honours" scandal. A leaked letter that he allegedly wrote to an aide of Mahfouz Marei Mubarak bin Mahfouz, a Saudi billionaire who had made a massive donation to Prince Charles's charity, revealed that he was offering support to the billionaire's application for citizenship. Mahfouz was made an honorary CBE (Most Excellent Order of the British Empire) in late 2016.

Prince Charles has distanced himself from the scandal, with a spokesperson of Clarence House saying, "The Prince of Wales has no knowledge of the alleged offer of honours or British citizenship on the basis of donation to his charities and fully supports the investigation now underway by The Prince's Foundation."

Meanwhile, a statement from the Prince's Trust read, "The Prince's Foundation takes very seriously the allegations that have recently been brought to its attention and the matter is currently under investigation. The scope of The Prince's Foundation investigation has been extended to cover this weekend's newspaper reports."

The charity added that the trustees had also already arranged an independent review by an external senior forensic accountant from a "big four" accountancy firm, reports Royal Central.

Meanwhile, a spokesman for Dr. Bin Mahbouz has also denied the reports, noting that 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."

Fawcett started his service to the British Royal Family in 1981 as a footman to Queen Elizabeth II, and later moved to the Household of her son Prince of Wales where he rose to become the royal's personal valet. He has previously resigned from Clarence House twice over allegations of bullying and mismanagement, but returned on both occasions with a promotion instead.

It is said that his proximity to Prince Charles is what protected him both times. The heir apparent reportedly once said about him, "I can manage without just about anyone, except for Michael."

Former royal press officer Dickie Arbiter also remarked of Fawcett, "Fawcett has been there for so many years, so close in times of stress, that he knows all the ins and outs and all the warts."

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Prince Charles Chris Jackson - Pool/Getty Images