Richard Osman says he felt like he was “cheating” on his beloved Thursday Murder Club characters when writing his new standalone thriller.

The four novels in his series featuring former spy Elizabeth, ex-union activist Ron, former nurse Joyce and retired psychiatrist Ibrahim, who meet weekly to solve cold cases at a luxury retirement village in Kent, have all been global bestsellers.

They are being brought to life in a Netflix film produced by Steven Spielberg and directed by Christopher…