How could I refuse the Queen when she asked me to set a Roy Grace thriller in London?

As his 21st bestseller takes the Brighton detective into the heart of Buckingham Palace, Peter James on the extraordinary friendship with Her Majesty that has inspired his new book

- BY MATT NIXSON

ROY GRACE creator Peter James recently spent the day working as a concierge at the iconic Grand Hotel in Brighton. But having sold more than 23 million books, it wasn't because he needed the cash. That said, he chuckles when he tells me: “I did get a fiver tip for carrying an elderly couple's luggage out!”

The prolific author was, in fact, researching the as-yet-unfinished 22nd novel featuring his Brighton-based cop, much of whose action takes place in, you guessed it, a major (fictional) hotel on the seafront of the bohemian East Sussex city.

It's a very Peter James thing to do.

Old school and exhaustive in his research, he famously seeks out people and experiences to help him make Grace's exploits as head of major crime for Sussex Police as thrilling - and realistic - as possible.

No wonder the series is such a hit.

It celebrates its 20th anniversary this year, with an acclaimed ITV adaptation - starring John Simm as the titular DS Grace and Richie Campbell as Detective Glenn Branson - having just wrapped filming of its sixth season.

Which brings us neatly to his current bestseller, the 21st Grace book The Hawk Is Dead, and the extraordinary “pinch myself” circumstances surrounding its writing.

Among the characters populating Peter's fictional world are two rather famous real-life personages - namely King Charles and Queen Camilla. And much of the drama takes place in, you guessed it again, Buckingham Palace.

It's a brilliant wheeze and the plot - featuring the Royal Train, an assassination bid, art thieves and a dramatic chase through the palace - is as drum-tight and compelling as ever. But how on earth did he get the royal seal of approval?

He admits with a smile: “I'm absolutely certain no other author has written a novel featuring King Charles and Queen Camilla and shown the inner workings of Buckingham Palace and the Royal Household as I've done.”