I’m standing outside Peel Castle on the Isle of Man contemplating the hill opposite. It’s an unseasonably hot September day and I’m overdressed in a woolly jumper and hiking boots. I’m here to locate a particular bench with curlicued arms. This bench drew Agatha Christie’s attention when she visited the Isle of Man.

I spot my target: the platonic ideal of benches, perched majestically on the hill’s brow, offering an interrupted view of the bay. Off I set, camera in hand. As I huff and puff my way up Peel Hill, pursued by territorial sheep, other benches loom into view. Many, many other benches. The hill’s absolutely heaving with them. All are of a modern ilk, clearly not originals. Not a single specimen’s curlicued. What even is a curlicue? Which bench was Christie’s chosen sit? It’s impossible to tell. She took reams of notes during her visit but even Christie scholar John Curran, who’s spent years deciphering her notebooks, can’t make head nor tail of her notoriously illegible handwriting in the Manx section of Notebook 56.

I go with my gut, snapping a photo of the bench that first caught my eye. I tick Peel Hill off my to-do list. Only 13 more places to track down before I fly home in two days’ time. I swing into Davison’s for two scoops of their world-famous ice cream, then it’s off to the lighthouse at Point of Ayre, Bowie blasting from the speakers of my little hire car. I might look like I’m on holidays but I’ll have you know, this is a quest.

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I’m here to follow in Christie’s footsteps.