It could have made him a billionaire – well, even more of a billionaire than he already was.

But when Bill Gates’s engineers brought him an e-reader in 1998, he told them to forget about the ‘unimportant’ device.

The Microsoft founder rejected the gadget, which featured a touchscreen, because he thought the future lay with keyboards.

Today, most modern gadgets eschew physical keys for touchscreens – although the original Amazon Kindle, which has fuelled the e-book boom, did indeed include a keyboard.