Ra and Anubis have set up a limited company manufacturing and selling Sundials. Initial business has been encouraging, with a number of orders received. They have called their company "Coca-Cola Sundials."They have a received a letter from Coca-Cola's head office in Atlanta, Georgia, USA stating if they do not stop trading immediately, they will "sue the company and put it out of business." Advise Ra and Anubis whether they have committed the tort of passing off and explain any defences they may have.