THE mysterious Somerton Man may have been killed by his nurse lover - an Adelaide woman and suspected Soviet spy with whom he fathered a child, it has been claimed.

And, in another startling revelation, two women who believe they are related to the Somerton Man's son want the unknown man's body exhumed in a bid to prove DNA links and in turn answer a 65-year-old que­stion as to his identity.

Tonight 60 Minutes reveals for the first time that the Somerton Man was romantically linked to Somerton Park nurse Jessica Thomson who lived in Moseley St, just metres from where the man's body was found slumped against a sea wall 65 years ago.

Her daughter, Kate Thomson, says she accepts her mother was a Soviet spy who may have had a hand in the murder of the Somerton Man, also a suspected Russian agent.

"She had a dark side, a very strong dark side," Kate tells 60 Minutes.

"She said to me she, she knew who he was but she wasn't going to let that out of the bag so to speak. There's always that fear that I've thought that maybe she was responsible for his death."

Police linked Jessica Thomson to the Somerton Man seven months after his well-dressed corpse was found on December 1, 1948.

But Jessica denied any knowledge when questioned by police. Kate says her mother lied to police.

"She told the police that she didn't know who he was and certainly I know nothing," Kate tells 60 Minutes.

"She did (know) and she told me that it is a mystery that was only known to a level higher than the police force."

The Somerton Man is one of Australia's most enduring and baffling Cold Case mysteries since his body was discovered on December 1, 1948.

According to 60 Minutes he was last seen knocking on the door of Jessica's house but she was not home.

He walked in the direction of Somerton Beach where his body was later found lying against a seawall.

Numerous items were found in his pockets, including a used bus ticket an unused rail ticket to Henley Beach. All labels to his clothes were cut off. His wallet was missing.

He died of unnatural causes, most probably due to poisoning.

Police later found a piece of rolled-up paper with the words "Tamam Shud", meaning "it is finished", found deep in a fob pocket sewn within the dead man's trouser pocket.

It was torn from a copy of the Persian book The Rubaiyat of Omar Khayyam - which was thrown into a doctor's car, parked outside his home at Somerton Beach, on the night of November 30, 1948.

The book had Jessica's unlisted phone number inside.

All police records relating to the case have been destroyed and Jessica, the one tangible link to his identity, is dead.

Jessica also had a son, Robin, to another man.

Robin's wife Roma Egan and their daughter, Rachel, have now come forward claiming Robin was the progeny of the Somerton Man and Jessica Thomson.

They are backing a new bid by Adelaide University physicist and Somerton Man expert Professor Derek Abbott to exhume the Somerton Man's body from his West Terrace Cemetery grave.

"It may be confronting, it may not be pleasant but I'd rather find out the truth," Rachel tells 60 minutes.

"Somerton Man is potentially my grandfather. So that to me is very important."

Prof Abbott has lodged a fresh application with Attorney-General John Rau to have the body exhumed.

"The imperative to identify this unknown man is on par with the current practice of identifying unidentified WWI and WWII graves for bringing closure to their families, and there is a considerable general public interest in the case to do so," he wrote in the November 21 letter to Mr Rau.

"In terms of specific public interest, there is a potential descendant of the unknown man living in Australia and I am now able to verify a compelling likelihood of this based on both historical proximity and anatomical evidence."

In October 2011, Mr Rau rejected a similar application stating that there needed to be "public interest reasons that go well beyond public curiosity or broad scientific interest".

THE SOMERTON MAN MYSTERY

ON November 30, 1948 an unknown man arrives in Adelaide on a one-way train ticket.

He buys another one-way ticket to Henley Beach and leaves his suitcase at the Adelaide Railway Station.

He doesn't take the train, instead crosses North Terrace and takes a bus to Henley Beach.

He's seen knocking on the door of nurse Jessica Thomson's Moseley St, Somerton Park, home that afternoon.

She does not answer and he walks towards Somerton Beach.

His dead body is found propped up against a seawall at 6.45am on December 1.

In his pockets were a used bus ticket, an unused rail ticket from the city to Henley Beach, a narrow aluminium American comb, a half-empty packet of Juicy Fruit chewing gum, an Army Club cigarette packet containing Kensitas cigarettes, and a quarter-full box of Bryant & May matches.

A half-smoked cigarette was balanced on his shirt collar.

A post-mortem revealed a fit man with broad shoulders, toned legs and a healthy heart. The pathologist suspected an exotic poison, but no trace was found.

On January 14, 1949 an unclaimed suitcase believed to be his - is found in Adelaide Railway Station's cloakroom.

Among items inside were a red checked dressing gown, slippers, underpants, pyjamas, shaving items, trousers, a screwdriver, knife and scissors. A coat had a front gusset and stitching only used on garments made in the US.

On April, 1949 police find a tiny piece of rolled-up paper with the words "Tamam Shud", meaning "it is finished" found in a fob pocket sewn within the dead man's trouser pocket. A doctor comes forward, saying it was torn from a copy of the book The Rubaiyat of Omar Khayyam - which was thrown into his car, parked at Somerton Beach, on the night of November 30.

This led to claims the man could have been a Soviet spy but supposed codes in the book were never able to be deciphered.

On June, 1949 a coronial inquest is unable to determine cause of death and an open finding is delivered. The man is buried at West Tce Cemetery.

In October 2011, the South Australian Attorney-General, John Rau, denied a request for exhumation.

WATCH THE FULL STORY ON 60 MINUTES, 7.30pm TONIGHT ON NINE.