Moment man who was adopted as a baby discovers his biological mother's identity and horrific past

A man that was adopted as a baby recalled the time that he discovered his biological mother's true identity, and was shocked.

Neil Berriman, from Petersfield, Hampshire, appears in a new BBC documentary, recalling the story behind his real family.

The Brit appears in the first episode, which is set to air on Wednesday (6 November) at 9pm.

Recalling that his adoptive mother Audrey had given him a brown envelope and instructed him to open it when he was older as it had 'the answers to some questions', he was uninterested - until she insisted.

On her deathbed, he said that the answers were there 'when he needed them'.

It took him three years after she died of cancer, but looking in the envelope, he found a document about his adoption and a newspaper article from 1994, detailing that the woman that he thought was his sister, was really his mother, report the Daily Mail.

Neil couldn't believe he was linked to the murder case (BBC)

But 17 years ago, Neil said he only knew of the Lucan affair, but it turned out that he was directly linked to it - that being that his mother was actually Sandra Rivett.

Sandra was just 29 when she was found dead in a mail sack in the basement of Lord Lucan's home in Belgravia, London.

He was the son of Lord Lucan's murdered nanny, and on the new documentary, he broke down in tears as he remembered the moment where he found out the identity of his biological mother.

Neil first discovered on the adoption order that his real name was Gary Roger Hensby.

Following her death, Lucan went on the run, and was last spotted at the home of Ian Maxwell-Scott, in Uckfield, Sussex, where he told his friend's wife that he went through a 'traumatic night of unbelievable coincidence' and was going to 'lie doggo for a while'.

Lord Lucan has been presumed dead since 2015, and he was never brought to justice for Sandra's murder, though an inquest 40 years prior found him guilty of murder.

Neil went on to explain: "So Stephen - the boy from the newspaper article - must be my brother. But (the nanny) can't be connected to me because she's called Sandra Rivett.

"I read the article one last time and down (at) the bottom I then realised her name was actually Sandra Eleanor Hensby."

Fighting back the tears, he stated: "I am the son of Sandra Eleanor Hensby - also known as the nanny murdered by Lord Lucan in 1974.

"A single letter is what I was expecting. This just doesn't happen, does it?

"The chances of you being adopted and finding out that your mother is [involved] in one of the biggest murder mysteries of all time. It's unbelievable," he admitted.

Neil is the son of Lord Lucan's nanny (Terry Fincher/Daily Express/Hulton Archive/Getty Images)

After giving Stephen up for adoption to her parents shortly after his birth, Neil was born two years later in 1966, and the adoption agency revealed that Sandra 'did not feel she could possibly bring this baby up properly herself'.

She had the child with a married man that had employed her as a housekeeper, though later married Roger Rivett the following year.

Sandra worked for Lord Lucan and his wife for 10 weeks before being murdered.

On 7 November that year, as Lady Lucan was watching TV, she was struck over the head a number of times, and fell to the ground, as the attacker told her to 'shut up'.

She recognised him as Lord Lucan, and bit his fingers whilst 'grabbing his genitalia', according to reports.

When she asked where Sandra was, he firstly said that she had gone out, before revealing: "I've killed her, she came down first, if it had been you, you would have got it'."

Lady Lucan then convinced her husband to help clean her injuries up, but as he went to the bathroom, she ran to a local pub and the report detailed: "She collapsed on the floor and screamed, 'He's murdered the nanny and he's after the children'. The police and an ambulance were called."

"The first officers on the scene spoke to Lady Lucan. She told them that the nanny had been murdered and she gave them her address. Lady Lucan was taken to St George's Hospital, SW1," it further read.

Lord Lucan had fled to Sussex, never to be found again, despite police investigations and he is presumed dead.