The late Queen gave the Duke of York her blessing to use his HRH title, The Telegraph understands.
Prince Andrew was permitted to use the title “in a private capacity” after it was announced that his military titles and royal patronages would be returned to the monarch at the height of the Jeffrey Epstein scandal.
He is now said to be determined to resurrect the privilege after the King allowed him to start pursuing certain business interests.
The Duke remains contrite about his perceived misdemeanours and has long considered himself hard done by for being effectively sacked as a working royal, despite having not been found guilty of any crime.
Throughout the Epstein scandal and ensuing civil court case, when he stood accused of raping and sexually abusing a teenager on three separate occasions, the late Queen proved one of her younger son’s most loyal and unwavering supporters.
'He talked her around and she agreed'
The Duke is said to have asked her if he could use his HRH title and after many tete-a-tetes at Windsor Castle, she conceded.
“She was always in his corner and he had her ear, of that there was never any doubt,” a source said. “He was not stripped of the title and was still able to use it privately. He talked her around and she agreed.”
The prospect was not welcomed by palace aides, aware that any use of the title would raise eyebrows, not least after the Duke had paid millions to settle the case out of court and was meant to be keeping a low profile.
A tentative plan to test the waters in public was thwarted, however, and the Duke was never afforded the opportunity to use the title before his mother died last September.
His future now rests in the hands of the King, with whom he enjoys a very different relationship.
King 'highly unlikely' to support move
While personally supportive of his errant younger brother, Charles is considered highly unlikely to support such a bold move, not least one that might indicate a return to the royal fold or risk jeopardising the reputation of the monarchy.
The King is thought to have held talks with the Duke in recent weeks, aware that his ostracisation posed a problem that was going nowhere and that the 62-year-old Duke needed some purpose.
He is said to have agreed to allow him to pursue some business interests, which would serve the dual purpose of keeping him occupied and allowing him to make some money.
As tensions thaw, he is understood to be considering permitting him to use his HRH title on correspondence, which would prove a huge boost to the Duke; restoring status and credibility.
An olive branch was also extended at Christmas, when the Duke was allowed to join the Royal family on the traditional walk to church at Sandringham, a move considered a gentle test of public opinion.
The concessions were welcomed by Prince Andrew but he continues to argue that he should be allowed to use the HRH title with which he was born.
Although he eventually accepted that he will never again undertake royal duties, he remains a Royal Knight of the Garter and had hoped to appear in public at last year’s Order of the Garter ceremony before a last minute intervention from the now King and the Prince of Wales.
Before his mother died, he had been lobbying the monarch for his status to be restored and wanted to be included at royal and state events.
The Duke vigorously defended himself against the sexual abuse civil case brought by his accuser, Virginia Giuffre.
Last January, Buckingham Palace announced that he had been stripped of his military titles and had agreed to no longer use his HRH title in any official capacity.
Just weeks later, he settled the civil case out of court with a $12million payment to Ms Giuffre, including a donation to her sex trafficking charity.
Buckingham Palace declined to comment.