TESLA and SpaceX founder Elon Musk once sacked his long-term executive assistant because she asked for more money. But it was the way he did it that was particularly brutal.

In a 2015 biography of the eccentric billionaire, Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future, journalist Ashlee Vance tells the story of how Musk had parted ways with Mary Beth Brown, known as MB, the previous year.

Brown, who had worked with Musk for 12 years, was likened to a real-life Pepper Potts to Iron Man’s Tony Stark.

“If Musk worked a 20-hour day, so too did Brown,” Vance writes.

“Over the years, she brought Musk meals, set up his business appointments, arranged time with his children, picked out his clothes, dealt with press requests, and when necessary yanked Musk out of meetings to keep him on schedule.

“She would emerge as the only bridge between Musk and all of his interests and was an invaluable asset to the companies’ employees ... For a short time, Brown’s duties extended to managing SpaceX’s books and handling the flow of the business in Musk’s absence.”

One technician interviewed for the biography said Brown “pretty much called the shots”: “She would say, ‘This is what Elon would want.’”

The problems started when she went to ask for a significant pay increase.

“Brown went to Musk and asked that she be compensated on par with SpaceX’s top executives, since she was handling so much of Musk’s scheduling across two companies, doing public relations work and often making business decisions,” Vance writes.

“Musk replied that Brown should take a couple of weeks off, and he would take on her duties and gauge how hard they were. When Brown returned, Musk let her know that he didn’t need her anymore.”

According to Vance, Brown, who was “still loyal and hurt”, didn’t want to discuss the episode for the biography. Musk, for his part, “said that she had become too comfortable speaking on his behalf and that, frankly, she needed a life”.

Musk explained to Vance: “I told her, ‘Look, I think you’re very valuable. Maybe that compensation is right. You need to take two weeks’ vacation, and I’m going to assess whether that’s true or not.’

“Before this came up, I had offered her multiple all-expenses-paid vacations. I really wanted her to take a vacation. When she got back, my conclusion was just that the relationship was not going to work anymore. Twelve years is a good run for any job. She’ll do a great job for someone.”

Musk gave her 12 months’ pay and never spoke to her again, according to the book. But in a series of tweets on Thursday night, the entrepreneur took issue with the anecdote, describing it as “total nonsense”.

“Of all the bogus anecdotes, this one troubles me the most,” Musk tweeted. “Ashlee never actually ran this story by me or my assistant. It is total nonsense. Ashlee Vance’s biography is mostly correct, but also rife with errors & never independently fact-checked, despite my request that he do so.”

Ashlee Vance's biography is mostly correct, but also rife with errors & never independently fact-checked, despite my request that he do so — Elon Musk (@elonmusk) August 11, 2017

Of all the bogus anecdotes, this one troubles me the most. Ashlee never actually ran this story by me or my assistant. It is total nonsense. — Elon Musk (@elonmusk) August 11, 2017

Mary Beth was an amazing assistant for over 10 yrs, but as company complexity grew, the role required several specialists vs one generalist — Elon Musk (@elonmusk) August 11, 2017

MB was given 52 weeks of salary & stock in appreciation for her great contribution & left to join a small firm, once again as a generalist — Elon Musk (@elonmusk) August 11, 2017

Writing on Quora in 2015, Justine Musk, Elon’s first wife, elaborated on the story. “Mary Beth Brown started working for Elon soon after we moved to LA twelve or thirteen years ago (Elon and I were still married then),” she wrote.

“MB was an exceptional and devoted employee of Elon’s and lovely to deal with on a personal level. She gave her life to the job — and to our family — and the news of her departure was a shock to me.

“Apparently (according, I believe, to Ashlee Vance, who wrote the book on Elon), MB asked for a raise. E told her that if she was truly critical to SpaceX, it should not be able to operate in her absence (or something to that effect). He suggested a three-week experiment to test this hypothesis/her worth.

“This reminds me of something similar he once said to me, many years ago, after I came back from a week’s visit with my family in Canada — that his life had operated quite smoothly in my absence. He was letting me know that I was an incompetent house manager. (He was not wrong.)

“So of the different stories I have heard behind MB’s departure from SpaceX, this is the one that resonates with me. (Although you would *never* use the word ‘incompetent’ in association with MB!)

“Wherever MB is and whatever she is doing, I hope her life is fabulous. She and I have not always been on the same side, but I have — and will always have — tremendous respect for that remarkable woman.”

frank.chung@news.com.au