Coronavirus has brought the Brexit negotiations to a virtual standstill, as both sides are preoccupied with dealing with the crisis and key figures have fallen ill. There are therefore growing calls for an extension to the transition period beyond the current date of 31st December 2020. Under the terms of the Withdrawal Agreement, any such extension would have to be agreed by the end of June. At the moment, the government is adamant that no extension will be sought or agreed to.

We can expect to hear much debate about that in the next couple of months, but as well as the question of whether to extend there is also the question of how long for. Given the uncertainties surrounding the pandemic, my own view is that longer is better. Indeed, a short extension would in some ways be worse than no extension at all, using up the one chance for flexibility without providing enough time to get the job done.

During the Article 50 negotiations that led to the Withdrawal Agreement, people may have got used to it being possible, if both sides agreed, to extend and re-extend by varying amounts as events required. Thus, although one of them is almost forgotten now, there were three extensions agreed: from 29th March 2019 to 12th April, then from 12th April to 31st October and finally from 31st October 2019 to 31st January 2020.

Crucially, there is no such flexibility in extending the transition period. Under the Withdrawal Agreement—which is a binding international treaty—there is provision for a single extension, which may be for one year or for two years.

So if the UK does come to the point of deciding an extension is necessary, and if the EU agrees to it, there will be only one opportunity to set its length. Given the unpopularity of an extension with many Brexiters, the government is likely to be tempted to make it of the shortest possible length.

Some have spoken of six months, or even a month-by-month rolling extension, although neither of these is compatible with the Withdrawal Agreement and therefore unlikely to be agreed to by the EU. So the choice probably comes back to one year or two.

If it were to be just one year, there is a very real possibility that this would prove to be too short. No one knows exactly how, or for how long, the pandemic will impact society, but there is surely every prospect of there being significant, widespread disruption well into 2021 and very possibly beyond.

The timescale for the transition period negotiations was already very tight and few with knowledge of such negotiations thought it was realistic. The issue is not just trade but all the other outstanding matters, such as security co-operation. Moreover, whatever the outcome of the trade negotiations, all of the necessary customs procedures and facilities will need to be developed and also all of the new regulatory systems, given the government’s plan to exit every single EU body by the end of the transition period.

As well as the ability of the UK and the EU to agree and implement all this, there is also the question of business preparedness. Again, this was already very tight under the current timetable. But with businesses having to deal with the massive disruption of coronavirus over an unknown timeframe, this problem becomes even more acute.

It is therefore highly unlikely that a one-year extension to the end of 2021 would be sufficient. But if, at the end of this June, that is all that has been agreed then there will be no mechanism for further extension. Prudence would therefore suggest agreeing the maximum extension of two years. If it turns out that this is over-cautious, then it does not need to be used. But it would be available if necessary.

None of this is about reversing Brexit. Brexit has happened now. Nor is it about being pro- or anti-Brexit. People on either side of that debate have an interest in Brexit now being done as smoothly and as effectively as possible.

No one could have predicted at the time of the referendum, or the last election, or the drafting of the Withdrawal Agreement that set the transition period, that we would face this pandemic. So there’s no shame in changing what was planned—and, after all, the provisions for extension were agreed precisely in case this was necessary. And there is much wisdom in doing so in a way that allows maximum flexibility. We only have one shot at this.