How the shamrock became the symbol of St Patrick’s Day

St Patrick’s Day is coming up and you know what that means… a Shamrock Shake at Starbucks, featuring those well-known Irish ingredients vanilla, mint and green tea. And then there’s the Paddy’s Day merch: shamrocks again. If the Princess of Wales as Colonel of the Irish guards turns up to celebrate the day, she’ll be sporting a sprig of it the size of a small broccoli.

What could be better as a symbol of all things Irish than this botanical metaphor for the Trinity? Because, as we all know, it was St Patrick who, to describe the triune God to the native Irish, picked a shamrock to demonstrate the Three Persons in one God. The point was lost on the authors of one children’s book on St Patrick I picked up in Dublin airport, which declared that what the shamrock showed was there were three gods in one, which is a) heresy and b) proof of what happens when nuns leave the education system.