"His relationships in the Middle East would make that an easier thing for him to do, not a more difficult thing."
It's hardly surprising given that the Prince of Wales' relationship with the community famously began at birth. He was circumcised by leading mohel Rabbi Jacob Snowman, instead of the Royal physician. He enthusiastically recounted his close friendship with Lord Sacks - whom he met on a plane to Rabin's funeral - at a dinner honouring the former chief rabbi. He was the first royal to attend a chief rabbi's inauguration ceremony - that of Ephraim Mirvis - at which he wore a blue velvet kippa with the Prince of Wales' feathers badge. And, speaking at a Holocaust Memorial Day event last week, he described the Shoah as "a warning to all of us".
Mayer, who describes herself as "three-quarters Jewish" because her maternal grandmother converted to Judaism, says: "He will be far more engaged with the subject than it's possible to imagine any previous monarch being.
"He's deeply devout; religion is incredibly important to him. Part of his philosophy is that there is a kinship among religions, that they're different expressions of the same truth, the same God; which is why he doesn't feel that they're at odds with each other. Interfaith and faith are hugely important to him. It has been mistaken for a New Age- lite form of religion. This adds to the fog of misunderstanding around him, the concerns that he's not a serious member of the Church of England - which, of course, he is."
We are speaking at the home Mayer, 54, shares with her musician husband Andy Gill (who has turned the ground floor of their flat into an impressive studio). An American, with a republican stance on the monarchy but politically a Democrat, she says she never took an interest in the Royal family. That was, until Prince Charles visited the Economist offices where she worked as a young journalist in 1985.
She recalls: "He wanted to discuss with people his own age how he might better use his position. That seemed such a fascinating thing to do. A man so famous, and yet he didn't know what to do with himself. It made me more interested in him. I've been gathering material on him for years."
However, Mayer has been accused by critics of overstating her access to the future King in writing the unauthorised biography. But the editor-at-large at Time magazine says she's been "incredibly transparent" in recording her access: a single, 30-minute recorded interview; a couple of walks; a seat at a fundraising dinner he hosted; and attending every public speaking event she could.
From this, she grasped his overwhelming charitable entrepreneurship. She says it's a side to Prince Charles, a patron of World Jewish Relief's Krakow Community Centre Project, which was lost to the public during the Princess Diana years.
She explains: "It was a polarising relationship and people joined one camp or the other. There was an assumption that the camps represented different values. Diana came to represent emotional intelligence, modernity and openness. He came to represent tradition, being emotionless, and of course, Prince Charles is very sensitive. He's been defined as being not like Diana, when in fact, he's actually quite like her. It impedes the public perception of him."
It was this relationship that brought about the book's title: "He's defined against Princess Diana and yet in so many key ways resembled her.
"She wanted to be the queen of people's hearts and I think, on some level, his aspiration would be to be the king of people's hearts. He would never put it that way, but it's where his instinct and impulses lead."
She adds: "It's interesting how pervasive the whole Diana thing still is. There's still a generation that remembers it very strongly. I went on a trip with Prince Charles and Camilla to Nova Scotia, with other journalists, and there was a warmth of feeling [towards them] but, in the crowd, people were always wanting to talk about Diana."
She believes the Diana scandal changed the monarchy for ever: "It lives on in the defensive reflex of the Palace system because they were so bruised by the experiences, and that impedes public perception of him."
But, she says: "Charles's charitable initiatives mean he's more accessible and communicative than his children are.
"William and Harry have still not forgiven the press because of what happened to their mother. It's famous among photographers that they will not actually do anything to facilitate them getting photos. They're retuning to a model of royality that is much more like the way the Queen does it."
And is Prince Charles ready to be King? "He's been ready for years - he's going to reshape the monarchy. He's not going to be like his mother. He has more opinions and active engagement in the world. He's going to mitigate them to the extent that he doesn't create constitutional crisis.
"Britain and the 15 other realms are going to get someone who has opinions and whose views are known. Whereas, with the Queen, it's quite hard to know what she thinks about anything."
She describes his book, Harmony, which is available on Amazon, as "a kind of manifesto. It's out there in a public domain and a lot of people haven't read it. I think it is essential reading.
"It explains why he feels so vehemently opposed to modernist architecture, it explains why interfaith work comes so naturally to him, it explains why he is so engaged with Judaism and Islam."
