This is an attempt to right a rock wrong. One of the most famous musical myths is simply not true.

The daughter of Mama Cass Elliot from folk vocal group Mamas and the Papas, Owen Elliot-Kugell, has a clear message to share about her mother’s cause of death: “There was a ham sandwich, but she didn’t eat it and she didn’t choke on it. So enough with the jokes.”

And there have been a lot of jokes, for almost half a century, including by Mike Myers as Austin Powers.

In the 1997 film, the time-switching special agent is writing a list of friends he knows in London and then scoring them out when he remembers they have died. After naming Jimi Hendrix and Janis Joplin he mournfully sighs: “Mama Cass. Deceased. Ham sandwich.”

Cass Elliot (Mama was a nickname which she preferred not to use later in her career) sang on some of the mid-60s most memorable singles, including California Dreamin’, Monday Monday and Dream a Little Dream. Her powerful voice was a crucial element of the harmonies that made the Mamas and the Papas so loved.

By 1974, she had gone solo and had just completed a two-week run at the London Palladium, when she died at the age of 32 in the Mayfair flat she had borrowed from her fellow American singer Harry Nilsson. The autopsy stated her cause of death as a heart attack and that there were no drugs in her system.

Her only child, Owen, was seven at the time and back at home in the US when she was told the news.

Now, ahead of the 50th anniversary of her mother’s death on 29 July, she has written a memoir My Mama, Cass, both as a tribute and as a way of correcting the sandwich-based inaccuracy.

“It’s beyond frustrating, almost immeasurable,” she says down the line from LA, explaining how it has been, having to live with the ham sandwich legend for 50 years.

“Even as a little girl, when I was hanging out with my friends at school, they didn’t know who my mom was, but I would go home to have playdates with some of these kids and it was kind of frequent that one of their parents would make a comment to me like, ‘Hey, did your mom really die choking on a ham sandwich?’

“It bothered me because it was such a horrible story, and I knew that it wasn’t true. And it just felt so cruel to have a rumour like that perpetuated. It tortured me.”

Understandably, she has done extensive work to piece together what did happen in the days leading up to her mum’s death; an itinerary which included playing her final Palladium show before “staying up for 36 hours”.

She was due to go to Mick Jagger’s birthday party all night, then head straight to a brunch thrown in her honour, followed by an afternoon tea hosted by a US journalist.

“By the time she got back to her flat, it was evening the following day,” continues her daughter. “She was hungry, and her dancer made her a sandwich from the only thing that was in the flat, ham, and left it on her bedside table. She never even took a bite.”

What also still upsets Elliot-Kugell is that the ham sandwich myth plays into another issue which was present throughout her mum’s life – weight.

From the age of seven Cass had battles with obesity. As a teenager she was prescribed amphetamines to speed up her metabolism.

Elliot-Kugell describes it as “the beginning of a very bad cycle.”

Crash dieting and drug taking would feature over the course of the rest of Cass’s life.

But what makes her so proud of her mum is the way that she “pursued and persevered until she made it.”

“She knew when she was a teenager that she wanted to be a performer and told everybody that she was going to be the most famous fat girl that ever lived. She had that forethought of knowledge as a child. I think that’s pretty cool. I think that’s really cool.”

A move from Baltimore to New York after school led to Cass becoming part of the Greenwich Village folk scene, before heading to Washington DC and then California, to join the Mamas and the Papas, but only after a delay due to the founding member, John Phillips, having to be persuaded that Cass’s weight would not hold the group back.

Eliot-Kugell believes that things would have been completely different for her mother if there had been the same attitudes towards fat shaming then that there are now, describing her as a “trailblazer”.

“She paved the way for these other young ladies nowadays who are of a heavier stature to break through in the music business and be accepted for who they are. I really do believe that she helped lay the groundwork for a lot of people.”

The book highlights examples of everyone from Dean Martin to her own band members making jokes in public about Cass’s weight, and how she would have to “grin and bear it” to survive, especially when it came to TV appearances.

By the early 1970s, Cass was regular on US variety shows, guest hosting the Tonight Show and regularly appearing on the Carol Burnett Show, but at a cost.

She would inevitably appear in skits making fun of her weight. Elliot-Kugell names one particular routine involving a “really heavy version of Little Bo Peep” as systematic of what her mum had to put up with to remain in the public eye.

Interestingly, she does, however, defend the line in the Mamas and the Papas hit Creeque Alley: “And no one’s getting fat except Mama Cass.”

“I really don’t believe that John Phillips wrote that lyric to be interpreted in that way,” she insists.

“You know how youngsters talk about things being phat? That’s like a bitchin’ thing, a compliment. I think I’d rather remember it like that. I want to believe that was how that was written.”

The memoir also deals with many happier subjects, with Elliot-Kugell sharing her own precious memories of her mother, including an afternoon in bed watching the Wizard of Oz, singing along together to The Carpenters’ Top of the World when it came on the car radio and what turned out to be their final farewell at LAX Airport.

“When she was in town, she was very involved,” is how she diplomatically sums up Cass’s mothering style.

She did not find out that her father was the session bass player Chuck Day, until she was 19 years old.

The book also reveals how Elliot-Kugell did finally find out, decades later, the true origin of the ham sandwich myth.

She was having lunch with her mum’s friend the journalist Sue Cameron and talk turned to Cass’s death.

“I said, ‘I really just wish I knew where that story came from’. She stopped eating, put her knife and fork down, looked me in the eye and said: ‘I did it’.”

Cameron went on to explain how back in 1974, when she heard the news, she called Cass’s manager Allan Carr in London to find out what had happened.

Elliot-Kugell picks up the story: “So many of her peers had passed away due to drug overdoses that Carr really wanted to protect her. And there was a sandwich that was found there.”

On the spot, Carr concocted the choking on a ham sandwich story and asked Cameron to write it up in the Hollywood Reporter to quell speculation until there was more information.

For Elliot-Kugell knowing the truth was a huge relief: “Allan Carr wanted to protect his client’s legacy and in a weird way it did. So now I understand, and it makes sense.”

She just wishes that everyone knew the truth.

My Mama, Cass by Owen Elliot-Kugell is released on 23 May.