Why is Tesco suing The Guardian?

Tesco has sued The Guardian and its editor, Alan Rusbridger, for libel and malicious falsehood over stories, comments and podcasts about the supermarket giant's tax arrangements. You'll find them here, and here and here and here. They reveal how Tesco has used offshore tax avoidance structures. And, of course, tax avoidance is a legal activity. So why has Tesco sued and what are the implications? That's the subject of my column in today's London Evening Standard.