I am writing this from a wonderful little former fishing village called Glengarriff, an hour and a half’s drive from the gleaming new Cork international airport. The economic success of Glengarriff is a good way of explaining why the DUP-Tory deal is so important to Northern Ireland, which for many years has struggled to keep up with the infrastructure improvements in the south. Today, while Belfast splutters, there is nothing less than an economic revolution going on in the south, thanks to European Union funding and a tourism boom that saw 2016 break all records. House prices in the south are now rising by €2,000 a month.