Journalist Robert Mulhern has spent three years investigating claims Kieran Kelly, a two-time convicted killer, has in fact murdered many more people - 31 to be exact.

Kelly's claims first emerged in 1983 after he killed his cellmate in London's Clapham Police Station, having been arrested for being drunk and disorderly.

Under questioning, the labourer from Ireland candidly confessed to strangling the prisoner - and then stunned officers by confessing to dozens of unreported and unsolved murders over the previous 30 years.

Kelly's victims died from stabbing, strangulation and blunt force trauma. Others survived being thrown in the path of trains on the London Underground.

Detectives believed they were in the presence of Britain's most prolific serial killer, yet Kelly's claims escaped public scrutiny for three decades.

Then in 2015, a former police officer alleged the murders had been covered up by the British Government.

A sense of urgency gathered around the case; a new investigation begged to be undertaken. Especially after it emerged that remains, thought to be human, had been discovered on the site of Kelly's one-time home in Ireland.

Against the backdrop of intense international media interest, London's then Metropolitan Police chief, Sir Bernard Hogan-Howe, committed to revisiting the case.

In this thrilling new book we cross two countries and three police forces in search of the truth.

Using new eye-witness testimonies, the case of Kieran Kelly has been methodically rebuilt, with new evidence gathered from a range of sources in Britain and Ireland.

Fighting a fog of contradictory claims, the narrative pursuit of _The Secret Serial Killer_ negotiates a series of curious twists before culminating in a bizarre showdown on the commons that Kelly himself once stalked.

Could Kieran Kelly have murdered 31 times?