The actor and comedian was giving a lecture at the Hay Festival in Powys, when he made the claims.

Fry criticised the "technophobes", including politicians, who he said had been too slow to react to developments like artificial intelligence.

The annual literary event began on Thursday with increased security.

Fry was delivering one of the Festival's Reformations lectures - one of a series of special lectures inspired by the 500th anniversary of Martin Luther's Protestant reformation.

"Whether it is winter that is coming, or a new spring, it is entirely in our hands so long as we prepare," he told the crowd in Hay-on-Wye.

"While it's hard to calculate the cascade upon cascade of new developments and their positive effects, we already know the dire consequences and frightening scenarios that threaten to engulf us," he said.

Science fiction writers and dystopians have already laid out the "nightmare" consequences, he added.

Fry went on to say a "great transformation in human society" was under way, greater than both the printing press and industrial revolutions.

It was "the greatest change to our way of living since we moved from hunting and gathering to settling down in farms, villages and sea ports and started to trade and form civilisations", he added.

"Whether it will alter the behaviour, cognition and identity of the individual in the same way that it is certain to alter the behaviour, cognition and identity of the group, is a hard question to answer.

"But believe me when I say that it is happening. To be frank, it has happened."

Fry-tech

The "war chests" of technology entrepreneurs were helping to fund the rapid development of artificial intelligence and robotics, he said.

Mr Fry revealed to the audience that he has an internet-connected fridge at his home in Los Angeles that allows him to check its contents via his mobile phone.

He also said he owned an automated car that allowed him to read a book or watch television as the car drove itself along California's freeways.

This year's 30th anniversary festival has 800 events and its line-up includes Graham Norton and US politician Bernie Sanders.

Festival organisers have asked visitors to allow extra time for arrival at the festival site and not take large bags or rucksacks, as extra security measures are in force in the wake of the Manchester terror attack.