Calcutta Cup: Why do England and Scotland compete for separate Six Nations prize?

Scotland and England battle it out for the Calcutta today - but what is it and why is the match played at the Six Nations?

from Daily Express :: Rugby Feed https://www.express.co.uk/sport/rugby-union/1239319/Calcutta-Cup-what-is-the-Calcutta-Cup-why-called-Scotland-England-Six-Nations-2020
via Express