She was accompanied by friends who, a little earlier, had dropped in to collect her from the commune where she lived at the time, in 1972, with her boyfriend.
After making their way across an empty building site, they stopped by the bamboos.
There, some of the group, mostly locals from Trinidad, including the self-styled Black Power leader Michael X – who had modelled himself on the militant black Civil Rights activist, Malcolm X — investigated a small hole in the ground before making it bigger with some tools.
They had enlarged it to the depth of about four feet when one of the diggers turned to Gale and asked: “What do you think this is for?”
She shrugged. “This is a fresh hole for decomposed bodies,” said the man before suddenly pushing her into it.
Two other companions began to lash at her with a cutlass. The swinging blade caught her hands and arms as she fought back, wounding her badly in the chest and throat.
Gale realised that they were trying to bury her alive. She was still breathing as mounds of dry earth was piled on to her body and the men she thought were her friends were frantically stamping their feet on it to keep her down.
The terrified Englishwoman couldn’t put up a fight for long and soon she passed out and died.
It wasn’t until seven weeks later that her badly decomposed corpse was discovered. Eventually the police brought those responsible to trial and the grisly details of her murder became public.
Gale’s murder came out in a Trinidadian court and two followers of Michael X were found guilty of her murder.
The tragedy was seen at the time as an extraordinary end for a mixed-up girl who had come under the thrall of a Trinidadian revolutionary, pimp, druggie and property racketeer.
But a new film raises disturbing new questions about why Gale was killed.
Was she simply a wide-eyed innocent, mesmerised by the energy and passion of her boyfriend and his black militant friends?
Or were more complex forces at play and was she actually killed, as the movie alleges, because she was a secret service agent on an undercover mission for MI6 whose cover was blown?
Gale was born with her twin brother, Greville, in London near the end of World War II in November 1944.
Her father was Captain Leonard Plugge, a radio enthusiast, inventor and Tory MP who had defeated future Labour leader Hugh Gaitskell in 1935 to win the constituency of Chatham in Kent, which he held for a decade.
He and his wife, Ann, already had one son, Frank, who was eight when the twins were born.
Today, Frank, 71, is the sole surviving member of that small family unit. He lives in Calais and remembers his childhood with great clarity.
Gale was, he says, “a happy child. She was lively and pretty, the opposite of her blond, quiet twin. Our father passionately believed that his children should learn languages and, because of that, he often insisted on a foreign language being spoken at the home dinner table and Gale was sent to the French Lycee in London.”
The privileged young girl’s early life was typical of someone of her breeding and generation; she began modelling, worked as a DJ for a French radio show and married young, at 20, to film director Jonathan Benson.
Their wedding was reported in the papers under the frivolous headline, “Silk, satin and lace,” in reference to her glamorous bridal attire. The actor Corin Redgrave, a friend of Jonathan, was the best man and the newly-weds moved into a big house in Chelsea.
However, it was not long before the marriage began to founder and Gale went away to Argentina. Her brother recalls: “I remember seeing her off. It was 1967, she was 22 and she just wanted to get away from it all, I think.”
After a short time, Gale came back. But the course of her life was changed completely by an encounter at a dinner party at the house of the actress Vanessa Redgrave (Corin’s sister).
There, Gale met an American who called himself “Hakim Jamal”, although his real name was Alan Donaldson.
He was from a broken home in a black district of Boston, had started using heroin at 14, been committed to an asylum for two attempted murders, and then underwent a spiritual conversion.
Hakim Jamal was clever, fiery, passionate about his political ideals and kept impressive company.
He talked of attending functions alongside Princess Margaret and her husband Lord Snowdon and the broadcaster David Frost.
Soon, Gale was mesmerised. “I didn’t like him at first,” she said later.
“He was very rude to everyone and kept calling us ‘white devils’.”
But she soon changed her mind. “He was the first black man I had ever really talked to. I was fascinated by what he had to say about black people’s suffering in the world.”
Her brother, Frank, saw a different side to the man with whom his young sister had become infatuated. “He was ghastly!” he recalls.
“Really cocksure. I mean, he used to call himself God.”
Hakim wrote a book about Malcolm X. Frank says: “I remember going to the launch party for the book, which wasn’t even at a publisher’s but in someone’s flat - full of all sorts of weirdos.
“But what I found really odd was the strange act Hakim did with Gale. He laid her across two chairs, head on one, legs on another, and as I watched, she seemed to go into a sort of coma. She was quivering — and she wasn’t acting.
Hakim said that being able to do this was proof that he was God.”
Having fallen in with this dangerous set, Gale was swept into the radical politics of the day, attending protest marches and attending a series of political rallies.
She was often short of money and her brother helped her out when he could. Once, she asked him to sell a writing box which their mother had given her.
Instead, he simply gave her the money for it and kept the box, in case she ever wanted it back.
Despite these problems, Frank didn’t see the trouble that was coming, and he never sat down with his younger sister and talked about the dangerous situation she might be getting into.
As part of the Black Power movement in London, Hakim was friends with Michael X, who had been described as “the authentic voice of black bitterness” and, in 1967, had become the first non-white person to be charged and imprisoned under the Race Relations Act for calling publicly for any black woman seen with a white man to be shot.
He had also set up a commune called “Black House” on the Holloway Road in North London which was financed by a young millionaire drop-out.
Michael X had many aliases — another name he used was Michael Abdul Malik — but was half-Portuguese, half-Trinidadian and his real name was Michael de Freitas.
He had arrived in Britain aged 24 on a cargo boat that docked at Cardiff and rapidly worked his way into the veins of criminal society.
He was a thug who managed prostitutes, ran gambling houses, sold drugs and became a rent collector for the notorious property racketeer Peter Rachman.
He once said: “They’ve made me the archbishop of violence in this country.”
John Lennon and Yoko Ono gave a bag of their hair to be auctioned to raise money for the Black House, in return for which they were given a pair of Muhammad Ali’s boxing shorts.
This was the sort of company Gale Benson was keeping. Soon, she changed her name to “Hale Kimga,” which had no cultural meaning but was simply an anagram of her own first name and Hakim.
Her friends simply assumed that Gale had become swept along by the excitement of the time.
But in the film, The Bank Job, out later this month, it is claimed that she was working deep undercover for the secret services as part of their campaign to infiltrate the Black Power movement.
To her brother, even with the benefit of hindsight, this seems a “ludicrous” suggestion.
“The details just don’t fit,” he tells me. He believes his sister had simply fallen in love, nothing more, nothing less.
In 1971, Gale and Hakim moved to Guyana. They had not been there long when they decided to move again, this time to Trinidad where, by this time, their friend, Michael X, was waiting for them, having fled England while on bail after being charged with extortion and robbery.
According to the film, Gale had an ulterior motive for being in Trinidad.
It claims that Michael X was using a set of sexually incriminating photographs of Princess Margaret, taken in Mustique, to try to blackmail the British Establishment.
Most of the pictures were allegedly stored in a bank vault in London, from where (according to the film) they were recovered in a sophisticated undercover raid by the intelligence services — the notorious unsolved Baker Street robbery.
Gale’s role, supposedly, was to see whether any other photos or negatives might be at Michael X’s home.
Whatever the truth, in late 1971, Gale and her lover moved into a house close to Michael X’s and began life on his commune.
It was a tight-knit community: Gale and Hakim ate in the commune with Michael every night.
But there were also some sinister incidents. For example, over the Christmas period, a group went to a nearby farm, slaughtered a cow and some drank its blood.
“They handed me the cup,” Hakim later attested, “but I ain’t no blood drinker.” A few days later, on the fateful morning of January 2, 1972, when Gale was killed, Michael X had been inciting his followers to slaughter and saying that he “wanted blood”.
By the time Gale’s body was discovered in the shallow grave, it was so decomposed that her twin brother could not make a positive identification and her dentist had to be flown in to confirm it was her.
A lengthy trial in Trinidad followed her cremation, and of the men present at Gale’s death, one turned witness for the prosecution, which is why so many details are known about how she died.
One of the group had drowned mysteriously at sea. A third, Joseph Skerritt, a local barber, had been murdered. Two more, Stanley Abbott and Edward Chadee, were eventually found guilty of her murder and given the death penalty.
One was hanged; the other had his sentence commuted to life imprisonment. Michael X, we shall come to in a moment.
But why did Gale die? When I ask her brother, Frank, he repeats again his absolute conviction that she was never a spy. Instead, clues come from the strange behaviour of Hakim. A month after her “disappearance,” he was given money by Michael X to leave Trinidad, an odd thing for someone truly in love with a woman missing there. After the discovery of her body, Hakim gave interviews to newspapers depicting Gale as a fragile, clingy soul, who had got on his nerves.
“She wanted to marry me and I knew then she was dependent on me for life,” he said in one particularly insensitive comment.
The writer VS Naipaul, who returned to his native Trinidad to research the incident, added weight to the picture of a woman who had simply begun to annoy those around her.
His article described Gale as “a fake among fakes,” documented her “slave-like” devotion to Hakim, commented acerbically on her unusual habit (as a white woman) of wearing African clothes and noted “she had a way of putting people off.”
So the theory that Gale simply fell out of favour with the black power commune and its influential, somewhat volatile, self-appointed leader, Michael X, seems most plausible.
There are no winners in this story – Hakim Jamal was shot in 1973 in Boston; and in a cruel twist Gale’s twin, Greville was killed in a car crash in Morocco that same year.
But Gale’s older brother Frank blamed Michael X for her death. And while the black revolutionary never faced trial for Gale’s murder, he was found guilty of that of the barber Joseph Skerritt, and was hanged in Trinidad in May 1975.
“I remember,” her brother Frank told me this week, “the day he was executed. I was in East Anglia, driving the car, listening to a programme on the death penalty, based around Michael’s execution which was due to happen at midday.
“I called in to the programme to talk about my own experience. And then, at noon exactly, I stopped the car, and heard it reported that he had died and I felt a great and overwhelming sense of relief.”
Finally, for Gale’s family, there was a sense that justice had been served.