In May 2020, Mary McKenna, founder and managing director of the twin travel agencies Tour America and Cruise Holidays, told me of the “tsunami” hitting her business. She also predicted correctly that the resumption of international travel would be suspended to the delivery of a Covid-19 vaccine.  One year on, she recalls the madness. “We had half our team working with no income coming in,” she says. “We refunded a good few million to our customers. And we did have some customers who said they’d keep their deposit on file for a later date.” The first thing she needed was…