The justification for a five-day break in Covid restrictions for Christmas was difficult before infection rates started spiking in the South East. Now, with the situation in London going “off the charts,” according to a Downing Street briefing to MPs, and the announcement that London will move into Tier 3 restrictions from Wednesday, the government’s Christmas plans now look near impossible.

Under Tier 3 rules, Londoners will be advised to “walk or cycle where you can and plan ahead to avoid busy times and routes on public transport”, and told to “avoid staying overnight outside of your area.” And yet, mere days after the capital’s restrictions come into effect, people across the country will be told it can travel over a five-day window to stay with family for Christmas. How will this be managed in the major transport hubs concentrated in London, and how can Londoners be reasonably expected to cancel within days Christmas plans which they were told would be fine several weeks ago?

The likely outcome will be that thousands of Londoners, understandably fatigued by Westminster’s mixed-messaging, leave city boroughs with some of the highest infection rates in the country to visit families in towns with the lowest rates. This would have disastrous consequences for local economies in regions where home working isn’t an option for many people, in addition to potentially fatal consequences for the parents and grandparents whom young professional Londoners will be visiting.

Further complicating matters is the fact that London’s outbreak appears to be fuelled by school children. Yesterday, schools in Greenwich, south-east London, were asked to close immediately after “exponential growth” of coronavirus cases among their students, with Danny Thorpe, the local council leader, telling headteachers that the situation “is now escalating extremely quickly.”

Since schools in England, unlike Wales, have not been asked to close a week before Christmas to allow a cooling-off period for contract-tracers, and given that Christmas involves children – many children, how will the government square school infection rates with allowing three households to meet during the festive period? The only logical solution would be to disallow the Christmas break in London, but that risks turning a period of national celebration into an ugly political battle, with the country divided into those allowed to do Christmas and those barred.

It’s easy to understand why Downing Street and the devolved administrations have planned to liberate the UK for five days over Christmas. It’s been an incredibly tough year. But the consequences of such short-term thinking could be severe and protracted. London’s severe outbreak – potentially the beginning of a third wave of infections across Tier 2 cities and towns in England – changes the equation.