Its obvious the EU is using this as an opportunity to flex their muscle as part of their overall strategy during the negotiations,it's too good to pass up, all they had to do was ring Macron and tell him to close the border under the guise of controlling the virus, meanwhile similar strain has been discovered in Italy, I'm pretty sure the French already had it and is covering it up.
Meanwhile they will enjoy watching Britain weaken, or so they think, unfortunately they have ignored history Napoleon, Kaiser and Hitler all found that the British people are not so easily cowed, it would only cause us to dig our heels in and become the ultimate awkward squad, something we're very good at.