B arring a reversal even more extraordinary than the many that have marked British politics recently, Sir Keir Starmer will be elected leader of the Labour Party, and therefore leader of the official opposition, tomorrow.

It is hard to recall a moment in our politics when a more effective opposition has been needed quite so urgently.

We will not be alone in hoping that Sir Keir comes to represent a politics of the centre that is socially just, green and internationalist. The Independent has been hungry for change for some time, hoping for a progressive alternative to a right-wing government and an extreme left-wing opposition. Sir Keir certainly has the virtue of being neither Boris Johnson nor Jeremy Corbyn.

Sir Keir may have fought a disappointingly unexciting campaign – calls for unity are all very well, but he failed to enlighten us on how he would bridge the deep divide between the wings of the party.

Now, however, such considerations seem to miss the point. For the past month, the people taking the lead in holding the government to account have been scientists and journalists, in particular at the daily Downing Street briefing. But even with a large government majority at a time of crisis – indeed, especially at such a time – the opposition should be able to hold the government to account as well.

That is a task that should suit Sir Keir, with his grown-up debating style, his attention to detail and his preference for persuasion rather than energising the already persuaded.

To be fair to Mr Corbyn, he has tried to strike the right balance between supporting the government at a time of national emergency and asking constructive questions. But he has too often slipped into partisan posturing, and his questioning has never been focused enough to apply any significant pressure on the prime minister.

Mr Corbyn’s claim to have been vindicated by the government’s economic response to the coronavirus epidemic was a typically tone-deaf reaction at a time of national tragedy. After his miserably poor election campaign, a period of silence from him would have been better judged.

For too long now, the quality of government in this country has suffered from the lack of a really testing opposition. Now the coronavirus crisis has exposed that weakness. We hope that Sir Keir’s election will start to change that. Even while parliament is not sitting, his public statements can help to add to the pressure on the government to raise its game on testing, ventilators and the effective deployment of NHS staff.

Beyond the immediate crisis, Sir Keir has a huge job of reconstruction to do. He will need to restore trust in Labour among Jewish people; he will need to develop a credible economic policy against the background of a post-coronavirus recession, in which he must seek to ensure that the burden is fairly shared; he will need a futuristic vision of environmental sustainability; and he will need to present Mr Johnson, Dominic Raab, Priti Patel and Michael Gove as harking back to the past.

It goes without saying that Sir Keir’s task for the next few years will be to keep Mr Johnson honest. That could be a long and thankless job, but it is a vital one, and one that needs to be done well if Labour is to have any chance at the next election.

Sir Keir Starmer in profile

That is probably still four years away, and Sir Keir will have a chance of winning power only if Mr Johnson stumbles. So far, with the crisis still in its acute phase, the prime minister has impressed the people with the tone and intention, if not necessarily the speed, of his early response. But he must be held constantly to the mark, and if he slips, Sir Keir’s record suggests that he could be ready as someone to whom the British people could turn.