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The Metropolitan Police said the decision followed advice from prosecutors and consideration of the information received to date.
It launched an investigation in February last year following a series of newspaper articles accusing former close confidant to the King Michael Fawcett of promising to help a Saudi billionaire donor achieve British citizenship and a knighthood.
Mr Fawcett resigned as chief executive of The Prince’s Foundation in the wake of the allegations.
But on Monday police said having interviewed several witnesses and examined more than 200 documents no further action would be taken.
A spokesperson for The Prince’s Foundation said: “The Prince’s Foundation has noted the decision of the Metropolitan Police.
“Following the conclusion of its own independent investigation and governance review last year, the charity is moving forward with a continued focus on delivering the education and training programmes for which it has been established.”
Anti-monarchy group Republic had made a formal complaint to Met detectives about Charles and Mr Fawcett in September 2021, following newspaper stories.
One article published by The Mail On Sunday featured a letter from 2017 in which Mr Fawcett reportedly wrote that he was willing to make an application to change businessman Mahfouz Marei Mubarak bin Mahfouz’s honorary CBE to a knighthood, and support his application for citizenship.
The letter, written on headed notepaper in Mr Fawcett’s then-capacity as chief executive of the Dumfries House Trust, said the applications would be made in response to “the most recent and anticipated support” of the trust.
Mr Mahfouz is reported to have donated large sums to restoration projects of particular interest to Charles. Mr Mahfouz is said to deny any wrongdoing.
The Met Police said in a statement: “A file was passed to the Crown Prosecution Service (CPS) on 31 October 2022 for early investigative advice. Offences under the Honours (Prevention of Abuses) Act 1925 and Bribery Act 2010 were considered.
“With the benefit of the CPS’s early investigative advice, and after careful consideration of the information received as a result of the investigation to date, the Met has concluded that no further action will be taken in this matter.
“Should any new information or evidence come to light that requires further assessment, this will be carried out by the Met’s Set (Special Enquiry Team).”
A Buckingham Palace spokesperson said: “We have noted the decision of the Metropolitan Police Service. All other inquiries are a matter for the Prince’s Foundation.”