From the Promenade in Portstewart, the town where I grew up, there’s a lovely view across the bay to the Inishowen Peninsula in Donegal. Somewhere along the Prom, Jimmy Kennedy, gazing over the water, wrote the lyrics to Red Sails in the Sunset, a song that’s been recorded by everyone from Bing Crosby to the Beatles. Portstewart is in Northern Ireland, Donegal in the Republic of Ireland — which my family always referred to as “the South”. As a glance at a map will tell you, though, Donegal is further north than Portstewart.

Peter Davidson doesn’t mention the perceptive oddities thrown up by a childhood in Ulster (unless I’ve missed something in the index), but in The Idea of North, now out in paperback (Reaktion Books), he deals with many other slippery notions of the essence of northness. His book, which I’ve just started reading, is a deeply researched and beautifully written survey of the concept of north in legend, history and the arts, and in the psyche of “northern” people. It makes a useful primer, too, for a trip I’m going on next month: by ice-breaker to the Canadian Arctic.