Four of the most powerful businessmen in the world – Jeff Bezos, Sundar Pichai, Tim Cook, and Mark Zuckerberg – are not used to having the tables turned. For more than five hours yesterday the tech barons, used to having much of the world at their beck and call, were grilled by the House Judiciary Committee of the US Congress in what turned into a highly political and combatative session.

The subject of the inquiry was whether these companies wielded monopoly power, something many on the committee made clear they saw as a threat not just to free markets but also free government and free speech.

With a report on the committee’s findings now due, this climactic set of testimonies gives a good indication of what we can expect.

There are five key takeaways.