I will agree with that. Tuesday/Wednesday were the days things changed rapidly in terms of Eurostar cancelling services and Boris making speeches advising not to travel.
My travel insurer is using 15th March for annual travel insurance - the day that a global pandemic was declared by WHO. That is a fair date at which to draw the line. Trips booked after that date are not covered for cancellation or disruption. Insurers seem to be offering cover for treatment for Covid-19, just not for cancellation or disruption.