Social distancing has made the British House of Commons feel a bit more like Dáil Éireann - a sparsely populated, echoing, business-like chamber in which the members are spread far and wide.

This has drained it of the special atmosphere that normally makes Prime Minister's Questions a box office event for political nerds (and set an artificially high bar of expectation for all other parliamentary debates around the world).

So what could have been a raucous occasion - the returning Boris Johnson facing his first Prime Minister's Questions from new Labour Party leader Keir Starmer - was turned into something rather different. Not a Punch and Judy show, but something altogether more revealing.

Instead of a Commons bear pit packed to overflowing, the atmosphere was more akin to a high court proceeding (with most of the witnesses appearing by video link). And that suited Starmer just fine.

Labour leader Keir Starmer

An experienced senior barrister, and former director of public prosecutions, forensic questioning is his stock-in-trade. By contrast, Boris Johnson revels in stirring up jeers and guffaws from the massed Tory ranks behind him. If the going gets tough, just crack a joke or hurl a jibe, and have the troops take over with some "atmosphere".

But when there are no troops, no backbenchers (or precious few), there is no atmosphere to rely on or hide in.

When all you have are the facts at your disposal, and there is a determined prosecutor two sword lengths in front of you, it's probably best not to antagonise the prosecutor because you will get found out very quickly, and there is no baying mob of backbenchers to cover up your discomfort.

That was the situation Boris Johnson found himself in today, as he returned to the dispatch box. And he had fair warning of what he would be facing.

Starmer's undramatic but steely slicing of Dominic Raab over the previous two weeks had left nobody in any doubt that for the first time in a decade, the Tories are facing a formidable opposition leader. And for Boris Johnson, he was engaging with this powerful force just at the moment that his conduct of the Covid-19 crisis is coming most sharply into focus as Britain pulls clear of the pack to lead Europe in the death statistics.

Starmer's technique is misdirection to start off talking about one thing, then suddenly changing tack with a sharp, dangerous question. Think of a matador, hiding his sword behind the cape but without the strutting and posing, just the lethal precision.

So, after welcoming the Prime Minister back to work after his brush with Covid-19, and congratulating him on the birth of his son, Starmer got straight down to work: "When the Prime Minister returned to work a week ago Monday, he said that many people were looking at the 'apparent success' of the government's approach.

"But yesterday we learned that, tragically, at least 29,427 people in the UK have now lost their lives to this dreadful virus. That is now the highest number in Europe and the second highest in the world. That is not success, or apparent success, so can the Prime Minister tell us: how on earth did it come to this?"

British Prime Minister Boris Johnson leaves 10 Downing Street for PMQs

To which Johnson replied: "First, of course every death is a tragedy and the right honourable and learned gentleman is right to draw attention to the appalling statistics, not just in this country but around the world.

"In answer to his question, I would echo what we have heard from Professor David Spiegelhalter and others: at this stage I do not think that the international comparisons and the data are yet there to draw the conclusions that we want."

At that point, the barrister produced exhibit A, a copy of one of the government's charts it has been publishing at the daily news conferences for the past several weeks showing the death toll in Britain and other countries, and saying: "The argument that international comparisons cannot be made, when the government have for weeks been using slides such as the one I am holding to make international comparisons, really does not hold water. I am afraid that many people are concluding that the answer to my question is that the UK was slow into lockdown, slow on testing, slow on tracing and slow on the supply of protective equipment."

Starmer then switched the focus of the attack to care homes, saying that while hospital deaths were starting to fall, care home deaths were still rising. Johnson said the care home death toll was in fact falling in more recent days, though he was careful enough not to enrage Starmer, wrapping the correction in candyfloss by saying that Starmer was "absolutely right to say there is an epidemic going on in care homes".

But Starmer QC came straight back with the stiletto: "I am grateful for that. I was using the slide the government put up at their press conference last night, which sadly shows, I accept, there is a lag to 24 April because of the reporting position that deaths in care homes have been rising every time they have been reported by the Office for National Statistics.

"I have heard before, from the First Secretary, that the numbers were falling - he said that a week ago Sunday. That is not borne out by these slides. We will wait to see what the next slides bring."

Even in a pretty empty chamber, perched high above in the socially distanced press gallery, you could sense the electricity in the moment; the new opposition leader landing jab after jab in a way Corbyn and Milliband before him could not.

And the shots kept on coming: "On 30 April, the government claimed success in meeting their 100,000 tests a day target. Since then, as the Prime Minister knows, the number has fallen back.

"On Monday, there were just 84,000 tests, and that meant 24,000 available tests were not used. What does the Prime Minister think was so special about 30 April that meant that testing that day was so high?"

With the abyss now open before him, Johnson took evasive action, talking about the "fantastic" testing regime that had sprung up in weeks, that Starmer himself had previously praised, and said the ambition was to get the testing rate up to 200,000 a day by the end of the month, thus handing the leader of the opposition more ammunition. Which he duly fired back.

"I am glad the Prime Minister has now said that the target now is 200,000 tests a day by the end of this month. But, of course, just having a target is not a strategy. What is needed is testing, tracing and isolation, that is the strategy.

"Contact tracing was happening in the UK, but it was abandoned in mid-March. We were told at the time that this was because it was 'not an appropriate mechanism', but yesterday the deputy chief medical officer said that it was to do with testing capacity. Can the Prime Minister clarify the position for us? Why was contact tracing abandoned in mid-March and not restarted sooner?"

Johnson was forced to concede: "As I think is readily apparent to everybody who has studied the situation, and I think the scientists would confirm, the difficulty in mid-March was that the tracing capacity that we had, it had been useful, as the right honourable and learned gentleman rightly says; in the containment phase of the epidemic was no longer useful or relevant, since the transmission from individuals within the UK exceeded our capacity".

"I think the Prime Minister has confirmed it was a capacity problem", Starmer replied, just like a barrister making sure the jury got the point.

This was an uncomfortable day in the office for Boris Johnson. Having become accustomed to the ineffectual questioning of Jeremy Corbyn, the Prime Minister got a thorough going over today without any raised voices or rowdy argumentation. Just skillful, precision cross examination technique.

He struck me as hesitant, perhaps nervous - certainly not the ebullient figure we have become used to. And it was not all the effects of recovery from Covid-19. Starmer was courteous in his style, not being seen to kick a man who may not have recovered 100% of his drive and energy. Johnson's replies were, by his usual standards, subdued and respectful.

He knows he has a very dangerous opponent, and avoiding a fight when there is a rapidly rising death toll is his best tactic, for the moment. Because one day, the fight will come. For Johnson, it is probably best carried out in a packed Commons chamber, with the rowdy atmosphere he thrives in.

For Starmer, the longer the Dáil Éireann/courtroom atmosphere holds, the better it suits his prosecutorial style. The evidence is mounting, the jury is listening. Boris Johnson may be about to go from political star to star witness whether he wants to or not. All because of a virus.

And that same virus has given Starmer the best possible start to his leadership of Labour. Without it, business as usual would be dominated by Brexit, and the looming deadline on a future relationship extension. Starmer would be on the thin ice of having been the main remain force within the Labour Party, prone to charges that his stance had cost the party seats in the north of England in the general election. He would have been starting out on the wrong foot. 

All the political momentum would have been with the Prime Minister and his massed ranks of Tory backbenchers in the house, and Tory supporting newspapers outside it.

But Covid-19 has turned the tables. Now it's Johnson who has to face critical questioning of his recent political past. And the questioning is coming from a professional questioner, a prosecutor by trade, at the top of his game. In a chamber that suits his style. Covid-19 has turned the House of Commons into an away ground for Boris Johnson.

In a Britain with possibly 55,000 excess deaths so far this year, a devastated economy and a population dislocated by the lockdown, hardly anyone cares about customs unions, tariffs and negotiations with Michel Barnier. They care about life itself. The game of British politics has just been re-set.