Relying on GPS has become second nature to most yachtsmen. I’ve met circumnavigators who do not even carry a sextant aboard. ‘You don’t need one,’ they say. What about when your power fails? ‘I’ll carry a hand-held spare’. What about when the batteries go flat? The forepeak will be stacked with AAs, they say.

And on Ebay you can buy GPS’s for under £30, so you could have two, three, four or more as back up.

Yet still I would feel that I’d shot an albatross and hung it round my neck for luck if ever I set off on an ocean passage without a sextant. A pal of mine said he’d done no astro before setting off on an OSTAR. ‘Once I got clear of the Western Approaches I picked up the book and taught myself how to do it,’ he told me. The book was Mary Blewitt’s classic on the art.

It must be this enduring fear of electrical failure – or at least of tempting the Gods by not having a sextant on board which sees a market for astro-learning still. This week a new book landed on my desk: Astronavigation from Square One by Alan Murray.

At least this will be an art of the ancients which will not be lost and forgotten – yet.