However, having written six books in the series, Yrsa has said, "I found myself unable to muster up the enthusiasm to continue, so I stopped".

But she didn't stop writing. She began a new series about police detective Huldar and child psychologist Freyja. The first in the series The Legacy (2014, translated 2017) won the Icelandic Crime Fiction Award.

Gallows Rock, the fourth in the Freyja and Huldar series, begins with the Icelandic president's staff reporting to police that a dead man, hanging from Gallows Rock, can be seen from the President's residence and they want the body removed before the arrival of the Chinese Foreign Minister on a state visit.

Gallows Rock, Galgaklettur, is an ancient place of execution in the Galgahraun lava field that "had formed thousands of year ago, long before any human had set foot in Iceland, when the Arctic Fox ruled supreme . . . there were fissures, craters spires of rock . . . it was a bleak, restless landscape".

Initially the police believe it to be a suicide, but a four-inch nail driven into the man's chest reveals it is a murder.

On the same morning, Freyja is called to an exclusive apartment block by reports of a child in distress. There, she finds a 4-year-old boy alone in an expensively furnished apartment. His name is Siggi and he wants to go home.

The apartment belongs to the man hanged at Gallows Rock, Helgi, an investment banker. There is no evidence to link Siggi to the murdered man, and while Huldar and his team investigate the murder, Freyja tries to find Siggi's parents, who seem to have disappeared.

Helgi's life, too, is a mystery. Despite his wealth, he lived alone and a search of news archives reveals nothing about him. Huldar wonders what he has done to provoke such a vicious attack.

In Hulda and Freyja, Sigurdardottir has created two attractive, empathetic characters, avoiding the current trend of the flawed detective. Huldar is good-natured, tolerant of his gay colleague, Gudlaugur, and supportive of Lina, a young women on work experience, the first of an intake of students taking the new degree in policing. Freyja is gentle and kind, helping her rogue of a brother adapt to life outside prison, while working at the Children's House, a refuge for abused women and children.

Gallows Rock is a skillful blend of a methodical police procedural with a dark, distressing story of domestic abuse and the role of social media in the sexual exploitation of women. It's a powerful combination.