Just imagine the possibilities.

Start with houses. London has a dozen properties listed on the market right now for more than £30m, according to Rightmove. You could buy them all – houses, plots of land, blocks of flats – for the £502m asking price, and barely touch the sides. You might not even notice the stamp duty of £50m or so.

Maybe flash cars are your thing. A 1954 Mercedes W196 sold in 2014 for a then-record $29.6m, before it was pipped to the chequered flag by a vintage Ferrari 250 GTO, which went for $38.1m. You could out-bid those buyers without breaking a sweat, and buy dozens more besides.

You could spend your money on the trip of a lifetime. An Italian businessman and a Chinese student each signed up for an epic adventure visiting 150 countries across two years in what was billed as the most expensive holiday in the world. But at a mere £1m, you could spend the next 100 years on them and blow just £50m of your remaining cash, so you would have to try a lot harder than that.

A brief trip into space with Virgin Galactic, assuming they ever manage to take passengers commercially, costs small change – just $250,000.

You have to think bigger than that. Dennis Tito, the world’s first ever space tourist, is said to be prepared to put $100m of his own money into a Mars project with a total cost of $2bn. You could fund the whole trip for less than half of your fortune.

A propsed trip to Mars is estimated to cost $2bn. You could afford that three-times over.  Photo: Getty Images

In fact, burning through the whole pile requires you to spend £1m every single day for the next 10 years, and you would still have £230m left. That is not an easy task.

Luckily, you will not have to try.

If you are ever the recipient of a $6bn slipup, you have no choice but to pay it back.

“Put simply, the general legal position is that someone who is given money by mistake should say what has happened and pay it back,” according to the Financial Ombudsman Service (FOS).

“But this may not be what consumers hear from friends or on the internet – where the informal advice might wrongly suggest that this is a case of ‘finders keepers’.”

In a case where the recipient genuinely believes the money is for them and has spent the cash before the bank or the person on the other end of the transaction notices, the FOS will then look at how you behaved when the money did arrive.

The end result is typically that the recipient has to make repayments either immediately, or in instalments if necessary.

So unless you regularly receive and spend $6bn payments, you can rule out counting on that excuse.

On the upside, if that cash stays in your account overnight, even in a current account paying 0.1pc interest per year, you would still rake in more than $16,000 for keeping it safe before the bank takes it back out of your pocket.