Queen Camilla has chosen a novel for her book club that imagines her husband King Charles, and other members of the Royal Family, being held hostage.

The Lords’ Day, which was published in 2007, is a tale about a security breach at the State Opening of Parliament.

Its author, Michael Dobbs, told the BBC he was “utterly surprised, overjoyed, very excited and rather deeply humbled” that his thriller had been selected.

He added that the move showed the Queen had “a fantastic sense of humour”.

In the book, the late Queen Elizabeth and the then-Prince Charles are among those held captive during a siege of the House of Lords.

It was “controversial” when it first came out, Dobbs said, because it talked about possible security flaws in Parliament.

But he said people eventually understood that he was not “writing a manual for terrorists”.

“I was writing a novel which gave solutions on security, and it helped toughen up that security,” he added.

Dobbs, himself a member of the House of Lords, has also written other books including the original House of Cards.

He sent a copy of The Lords’ Day to the new King and Queen about a year ago “for a chuckle”.

“I didn’t expect them to read it, they are busy people,” he added.

He learned about the inclusion of his book on The Queen’s Reading Room book list, as first reported by The Telegraph, about three weeks ago from his publisher.

“I was bowled over when I found out,” he said. “If you look at her previous choices, you have the likes of Dickens, Tolstoy, and some of the greatest modern authors on the list, and to have a Dobbs novel included was totally unexpected.

“The Queen is very serious about getting people to read, and opening up people’s minds, which is what books do best,” he added.

The King carried out the State Opening of Parliament for the first time as monarch last November, accompanied by the Queen.

The ceremony, dating back to the 15th Century, marks the start of a parliamentary session, bringing together the constituent parts of Parliament – the Crown, peers and MPs.

The Queen’s Reading Room launched as an online book club on Instagram, before becoming a charity last February.

It includes a list of reading recommendations from the Queen herself.

Other books on the list include Lessons in Chemistry by Bonnie Garmus, Girl, Woman, Other by Bernardine Evaristo, and The Year of Eating Dangerously, by the Queen’s son Tom Parker Bowles.

The organisation also hosts an annual literary festival and has launched a new podcast.

The BBC has contacted The Queen’s Reading Room for a comment.