It lasted four and a half hours and rather than Mark Zuckerberg getting a roasting, as predicted, it was more a light grilling.

The Facebook chief sat in front of 44 stony-faced US Senators in the first of a two-day congressional hearing into the data hacking scandal that has engulfed the company.

The lighter approach had a lot to do with several of the long term senators having very little knowledge of how Facebook worked. The joke going around was perhaps they would have been better off bringing in their grandchildren to frame the questions for them.

For example, Senator Orrin Hatch asked: “How do you sustain a business model in which users don’t pay for your service?”

A somewhat disbelieving Zuckerberg paused briefly, and realising it wasn’t a trick question replied “Senator, we run ads.”

Zuckerberg’s extraordinary amount of preparation for the hearing also paid off. During the past week Facebook created a mock-up of the hearing room in a conference room and then employees threw every imaginable question at the usually shy CEO.

The result? Zuckerberg, mainly, was allowed to stick to his well-rehearsed talking points while Senators at times struggled not to let on that they were generally in awe of his extraordinary business success.

Tomorrow it is Round Two where, in the same room, he faces a new group of questioners from the House of Representatives.

After today they should think about phoning their grandkids tonight to seek advice on how to land a solid punch on the, so far, undefeated champ.

The figures come as Facebook has lost more than $116 billion in market capitalisation amid the Cambridge Analytica scandal that has dented the social media company's reputation.

Days before the scandal came to light in February, Facebook's shares were trading at an all-time high of $USD 190.28. Two months later, investors had erased eight months of gains for Facebook, plunging the shate price down to $USD 152.22.

Today's closing price marks the highest Facebook's share price has been in three weeks.

Early in the hearing Zuckerberg revealed his surprise at how the Russians used his social media website to attempt to influence the US presidential election.

“One of my greatest regrets in running the company is that we were slow in identifying the Russian information operations," Zuckerberg said.

"We expected them to do a number of more traditional cyberattacks-which we did identify and notified the campaigns that they were trying to hack into them - but we were slow in identifying the type of new information operations.”

"This is an arms race. They're (Russia) going to keep getting better."

Questioned about how safe Facebook was, Zuckerberg, worth US$63.9 billion, said: “I think Facebook is safe. I use it, my family uses it and all the people I love and care about use it all the time.”

The warnings from senators came straight away: “If you can’t fix these huge problems we can bring in laws to make sure you do.”

Zuckerberg admitted in his opening statement that Facebook had made some big mistakes. “We didn’t do enough and did not take a broad enough responsibility” to protect Facebook users.

“It was my mistake, and I’m sorry. I started Facebook,” he said. “I run it, and I’m responsible for what happens here.”

That mistake, as one Senator after another pointed out, allowed the British company Cambridge Analytica, with links to Donald Trump’s election campaign, to get the personal information 87 million Facebook users taken without their consent.

Gone were the trademark grey T-shirt and jeans. For his Washington appearance (and the recent apology tour Zuckerberg has been on) he is now all suit and tie. 

Appearances are important in the Capitol so Facebook “fixers” having checked out the hearing room and ensured there was a booster cushion on his chair. The joke around the room, “to give his testimony a lift.”

Senator Bill Nelson asked why his company hadn’t warned the 87 million people their information had been stolen? Zuckerberg replied it was a mistake not to inform users because Facebook believed, incorrectly, that Cambridge Analytica had deleted the information.

Senator John Thune: “Facebook has a 14-year history of apologizing so why should we trust today’s apologies?”

Zuckerberg: “At the end of the day this is where people will measure us on our results from this. I am committed to getting this right. And by the end of the year we are going to have more than 20 thousand people working on security and content review at Facebook.”

As for the much talked about plan that there will soon be “a paid for version” of Facebook, Zuckerberg appeared to indicate that could happen.

“Are you actually considering having Facebook users pay for you to not use that information?,” Senator Nelson asked.

“In order to not run ads at all we would need some kind of business model,” Mr Zuckerberg said.

“I am going to have to pay you in order not to send me using my personal information, something that I don’t want?” Senator Nelson said.

“Yes, Senator,” he replied.

Senator Orrin Hatch: “Nothing in life is free. So, will Facebook always be free?”

Zuckerberg: “Yes there will always be a version of Facebook that is free. It is our mission to try to connect everyone around the world.”

If laws are then toughened to restrict Facebook’s use of personal information it will have a knock-on effect on others such Twitter, YouTube and Snapchat. After all, their core business model is to learn as much as possible about you the user and to sell targeted ads to you and new restrictions will make them less profitable.

But despite all these attacks on the internet’s golden boy (which will continue with another marathon hearing tomorrow) Zuckerberg’s job is safe.

Today he was not there fighting for his job. He totally controls the company; his board loves him. Instead he was fighting for Facebook’s popularity and reputation.