I’ve always been a bit suspicious of the Patrick legend. For example, it is claimed that he banished snakes from Ireland. This is dubious on two counts: first of all, there’s no evidence that there were ever snakes in post-glacial Ireland; secondly, Fianna Fail is still in business — and indeed running the country. The shamrock nonsense comes from the legend that St Pat, seeking some way of explaining the Christian doctrine of the Holy Trinity to my (dense) fellow-countrymen, came up with the wheeze of showing them a three-leaf clover. Seems that they fell for it, big time.