Branson's cola captured just 0.5% of the American market and had to cease US operations in 2001. The brand initially survived in the UK but was pulled from supermarket shelves in 2009 due to its waning popularity. Production halted in 2012 and the drink, a major flop, was consigned to history.

Read more on Branson's incredible investments that did work: From records to rockets: how Richard Branson made his billions

Rowling clearly had a drastic change of heart because just eight months after she bought it, the yacht was put up for sale at the vastly reduced price of $19.2 million (£14.7m) – $7.8 million (£6m) less than she paid. 

Perhaps Rowling should've bought one of these: Billionaire boats to blow your mind and your wallet

The ratings tumble is estimated to have cost the network $330 million (£252m). Fortunately, Winfrey has since managed to turn it all around, partly thanks to Tyler Perry, and her net worth is topping an impressive $2.8 billion (£2.1bn) at the current time.

Read about Oprah Winfrey's incredible rags-to-riches story

In fact, Tesla has lost over $10 billion (£7.7bn) in market cap since August, impacting on its CEO's net worth, which stands at $20.8 billion (£15.9bn). Adding to the tech tycoon's problems, Musk is now under investigation by the US Department of Justice over the tweet, which may have broken federal law.

Read more on the billionaire maverick: Elon Musk's incredible success story

Incredibly, Buffett believes that if he'd bought an up-and-coming insurance business instead, his holding company would be worth twice as much as it is now, a figure than runs into the hundreds of billions of dollars.

Not put off by their past mistakes, read about: Billionaires' extraordinary pet projects to transform the world