THEY like to brag that Irn-Bru outsells Coca-Cola in Scotland. “You could just count the number of bottles in the chiller cabinets in the shop,” said a veteran staffer at AG Barr, which makes the shocking-orange soft drink in Cumbernauld, northeast of Glasgow. “But the easiest way to find out who does best between us and Coke is to ask people on the street what their favourite soft drink is.”

That confidence is about to be put to the test. This week, AG Barr will tell the stock market about its plans to join forces with its larger rival, Hertfordshire-based Britvic, which makes Tango and Robinsons squashes.

The deal has been billed as a £1.4 billion merger but most in the City regard it as