If you wait for the evidence it's closing the stable door after the horse has bolted... this is a time when the precautionary principle can be justified.And no evidence of increased risk of severe illness.
I wonder if the variant had been found in Germany, what our reaction would have been. Can't see the rest of Europe rushing to impose travel bans before scientists had the chance to do their job.
We have treaty obligations with Germany in terms of free movement ... plus official channels where we and other European governments could press Germany to take action itself. We have neither with South Africa. And realistically given the extent of movement between Germany and other European countries, it's a different situation entirely... It likely would be too late by the time it was detected. South Africa vis a vis Botswana or Japan would be a reverse situation.