On a bitterly cold, foggy morning in October 1927, Mercedes Gleitze, smothered in olive oil and lard to protect her from the intense cold of the water, made history when she became the first British woman to swim the Channel.

And then, two weeks later, she had to do it all over again — to silence the doubters after a hoaxing scandal that captivated the world.

Now, the story of the intrepid Gleitze, the ‘hoax’ and that second so-called ‘Vindication Swim’ has been made into a film of the same name, starring British actress Kirsten Callaghan. And it is an extraordinary story.

Even before her feat, the glamorous Gleitze was something of a celebrity. Born in Brighton in 1900 to German immigrants, Gleitze moved to London after leaving school to become a stenographer. But her passion was open-water swimming, and she devoted all her spare time to practising in the Thames after obtaining special permission from the Port of London Authority.

Over time, Gleitze’s long-distance swims in the river became such a phenomenon that she began drawing large crowds. On one occasion, she almost drowned after being pulled under by strong currents at Westminster Bridge and had to be fished out by river police.

Mercedes Gleitze (pictured) made history when she became the first woman in history to swim the Channel. And then, two weeks later, she had to do it all over again — to silence the doubters after a hoaxing scandal that captivated the world

Kirsten Callaghan stars as the intrepid Glietize in the upcoming film Vindication Swim

The front page of the Daily Mail in 1927 with an advert for the Rolex Oyster watch which Gleitze endorses. The watchmaker would later acknowledge that she played a key role in establishing the company as a household name and, indeed, she went on to feature in many more adverts

In 1927, she swam from Westminster to Folkestone via the Thames and Kent coast, a total of 120 miles. Again, she almost drowned when she was pulled under river barges by the strong undertow.

However, it was the 21 miles of rough and unpredictable water separating the White Cliffs from Calais that were her real focus. Fewer people have swum the Channel than have climbed Mount Everest — the first person to do it was British steamship captain Matthew Webb, who made it on his second attempt, in 21 hours and 45 minutes, in 1875.

In August 1926, Gertrude Ederle, an American professional swimmer, became the first woman to make it across, in 14 hours and 39 minutes — much faster than Webb, since by then swimmers were no longer limited to breast stroke. She was followed by another American, Amelia Gade Corson, later that same year.

Neither of them captured the public imagination or the Press’s attention in the way that Gleitze did. Most contemporary women athletes had sponsorship or personal wealth behind them, but Gleitze was working class and self-supported.

Over five years, Gleitze made seven unsuccessful attempts to swim the Channel. Usually, it was the cold or bad weather that defeated her, but she was also badly stung by jellyfish, menaced by cramp and once surrounded by a thick swarm of flies.

She rarely gave up willingly. A 1926 swim was ended by her trainer, George Allan, who — fearing she was about to collapse and drown as she was already hallucinating — lassoed one of her arms and pulled her out. Gleitze’s pluck and determination impressed the watching world.

Few people at that time believed that women were truly capable of conquering the Channel. When Ederle did it, there were accusations that two accompanying tug boats, carrying her entourage and reporters, had protected her from the bad weather.

Gleitze in October 1927 during one of her unsuccessful attempts to swim in the Channel.  Over five years, Gleitze made seven unsuccessful attempts to swim the Channel. Usually, it was the cold or bad weather that defeated her, but she was also badly stung by jellyfish, menaced by cramp and once surrounded by a thick swarm of flies

Callaghan as Gleitze in Vindication Swim. The film is in cinemas on Friday

So, at 2.55am on October 7, 1927, Gleitze made her eighth attempt, starting from the French side at Cap Gris-Nez. Thick fog hung over the murky waters, while the sea was calm but a decidedly chilly 16c (60f). A small fishing boat from Folkestone led the way, sounding its horn to guide her out of the path of heavy shipping.

Wearing a tight rubber hat and motorcycle goggles, which impeded her hearing and vision, Gleitze was soon suffering from the extreme cold and intense thirst. Her trainer George tried to keep a conversation going over the side of the boat to stop her going to sleep, and gave her strong hot tea every two hours. For food he dangled grapes on a string hanging from a rod. ‘In the excitement of trying to catch them I forgot about being cold,’ she said later.

Unable to work out their position in the fog, Gleitze and her team had only the Dover gun — an artillery piece fired at intervals from the pier to warn ships of the proximity of land — and the siren of the South Goodwin Lightship to guide them as her pain and exhaustion intensified. Then, suddenly, a land bird alighted on the pilot boat and they finally heard the harbour foghorns.

‘When eventually I heard a loud shout from the boat, I felt a great hope surging straight through me,’ Gleitze said. ‘I let my feet go downwards gradually, and it was land. If I had not felt so weak, I should have cried with joy.’

At 6.10pm she staggered ashore, after 15 hours and 15 minutes in the sea, collapsing into unconsciousness in the arms of her trainer, and waking up in ‘pain too terrible to describe’ in the boat taking her to Folkestone.

She had triumphed — but, just a few days later, another British open-water swimmer, Harley Street doctor Dorothy Logan announced that she had made the same crossing in a mere 14 hours ten minutes.

The headlines were suddenly all about Dr Logan, although her claim was soon challenged and she admitted it had been a hoax — she had indeed set off from France, but her trainer had picked her up in his boat and then dropped her off three miles from the Dover coast.

Logan said she wanted to highlight how ‘anyone can say they have swum the Channel’. It was a mean trick since her remarks sowed a seed of doubt in many minds about Gleitze’s swim.

Even before her feat, the glamorous Gleitze was something of a celebrity. Born in Brighton in 1900 to German immigrants, Gleitze moved to London after leaving school to become a stenographer. But her passion was open-water swimming

In order, as Gleitze put it, ‘to restore the prestige of British women Channel swimmers in the eyes of the world’, she decided to do the swim again. She had no trouble getting witnesses — she was accompanied by an army of international journalists and photographers eager to witness the Vindication Swim.

But when she set off on October 21, there was considerable scepticism. The sea was even colder and one of the boats that shadowed her contained not only a jazz band (music kept up her spirits) but several doctors determined to pull her out of the water if necessary.

The world was listening, as news of her progress was transmitted by wireless around the globe by steam ships and aeroplanes. Reporters on the accompanying boat dispatched carrier pigeons to fly to land with updates.

As the sea temperature dropped to 10.5c (51f), after ten hours and 30 minutes, doctors advised her to abandon the attempt. But Gleitze, who’d spent three hours battling against an ebb tide trying to carry her in the wrong direction, swam away when she saw a ladder being lowered from a boat for her. They pursued her and, with the aid of a twisted towel thrown underneath her arms, she was pulled, protesting loudly, out of the water.

Back on land she said it had been a ‘terrible disappointment’, adding that she had been ‘cut by the iciness’ of the water from the start. But everyone agreed with Pathe News’ verdict that it had been a ‘splendid failure’ and left little doubt that her original successful swim must have been genuine — a view that was rubber-stamped by the newly formed Channel Swimming Association.

Rolex, which had given her a prototype waterproof watch to wear on the Vindication Swim, sealed her international fame by buying the entire front page of the Daily Mail to celebrate her and the ‘Oyster’ wristwatch she had hung from a ribbon around her neck and which was still working perfectly.

The watchmaker would later acknowledge that she played a key role in establishing the company as a household name and, indeed, she went on to feature in many more adverts. The Channel swim was only the start of Gleitze’s career. In 1928, she was the first person to swim the Strait of Gibraltar between Spain and Morocco — a shorter distance than the Channel, but harder, due to strong currents, sharks and numerous whirlpools.

The White Cliffs of Dover in Kent. The 21 miles of rough and unpredictable water separating the White Cliffs from Calais that was Gleitze real focus. Fewer people have swum the Channel than have climbed Mount Everest (stock image) 

Gleitze married Patrick Carey, an engineer from Dublin, in 1930, but instead of going on a honeymoon, she went off to swim across the Dardenelles (Hellespont) in Turkey.

The only stretch of water that proved beyond her was the North Channel separating Northern Ireland and southwestern Scotland in the Irish Sea. She made eight attempts on the 22-mile or so crossing, but was defeated by the cold. Gleitze rightly became an icon for female empowerment and was also a champion of social justice, donating much of her earnings to set up hostels for the homeless.

She went on to have three children, but in middle-age became a virtual recluse due to a debilitating genetic condition affecting her circulation.

She died in London in 1981, aged 80. According to her daughter, Doloranda, her mother’s secret was an inner calm that meant she was never overwhelmed by the intimidating vastness of the open sea.

‘I know no sensation,’ Gleitze once said, ‘but that of calm pleasure at the prospect of another tussle with those ‘calling’ waves.’

Vindication Swim is in cinemas from Friday.