The chilling words of a convicted murderer will soon be heard, back in time to a winter night in 1969, in a revealing newly recorded interview with one of the two brothers who kidnapped and murdered Muriel McKay. “Maybe the only solution is to go there. To be there again, I will have to retrace my steps,” Nizamodeen Hosein will say.

The notorious killer at the centre of a police investigation that dominated the news 55 years ago has suggested that a trip back from Trinidad and Tobago, where he was deported in 1990 after serving a 20-year prison sentence, could jog his fading memory of the location of the body of the 55-year-old woman he abducted from her Wimbledon home in an extraordinary case of mistaken identification.

Confirming that McKay’s body lies somewhere on the Hertfordshire farm he once shared with his late brother Arthur, Hosein has claimed he cannot remember what he last told police. The investigation was reopened this year after Hosein confessed three years ago and gave new evidence to McKay’s children when they visited him in Trinidad. Detectives also flew there to question Hosein in March this year.

Last month, an attempt by police to locate the burial site at Rooks Farm in Stocking Pelham failed. McKay’s son, Ian, who lives in Australia, was present at the exhumation, desperately hoping for a solution to the mystery. After the search, the victim’s family said they planned to ask the Home Office for permission for Hosein to fly back temporarily to revisit the crime scene.

Hosein, who spoke to BBC journalist Jane MacSorley this month, has now asked for another chance to help. “As I said, I have to go to the place to remember. So I can’t tell you from here,” he said.

On the evening of December 29, 1969, Hosein and his older brother seized the mother and her wife from their home, believing her to be Anna Murdoch, the second wife of media magnate Rupert Murdoch. McKay’s husband, Alick, was a senior colleague of Murdoch’s at the Sun and had borrowed his boss’s car. McKay’s own vehicle was being repaired, so Murdoch had offered to let him use his chauffeured Rolls-Royce while he and Anna spent the Christmas holidays in his native Australia.

The Hosein brothers followed the Rolls-Royce in their mud-blue Volvo and wrongly identified the house where they thought the wealthy newspaper owner lived. They took Muriel with them, leaving the house empty for her shocked husband to discover when he returned from work.

This summer, MacSorley re-examined the case for Radio 4 in her podcast Worse than murder: The final two episodes will be released on BBC Sounds this Monday and next week, and will be broadcast on Radio 4 on Wednesday 28 August and Wednesday 4 September. They will provide stark new conclusions about police failures in handling a ransom demand from the brothers, who called themselves “M3” in a series of gruesome phone calls to the McKays’ home.

Muriel’s children have told MacSorley that no financial help has been offered to the family to bring them any closer to meeting a £1m claim from M3, worth the equivalent of £14m in today’s money.

A series of failed police attempts to capture the kidnappers, including one in which dozens of police cars converged on another Hertfordshire village, are said to have delayed the Hoseins’ capture. They were eventually tracked down by their number plate and arrested at the farm, before being jailed in 1970. Muriel McKay was never found.

In the last episode of Worse than murder, MacSorley accuses Hosein of prolonging the McKays’ suffering. “I’ve been a journalist for over 30 years,” MacSorley said. “I’ve interviewed pedophiles, rapists, murderers … But I’ve never interviewed anyone like Nizamodeen Hosein. He came across to me as a troubled and misguided man, with no sense of remorse.”