Like most things, I think it dates back to when I was a child.
On a still, cold night, I would lie in my bed with all the windows open and strain to hear the sound of mainline trains heading through the station on the other side of town.
Sometimes I was unlucky and would fall, eventually, into an disgruntled sleep. But on occasions I would catch the faint two-tone cooing of a horn, calling from several miles away, but as clear and bewitching as the hooting of an owl in our back garden. And I would drift off, somehow calmer and more carefree, as if reassured that somewhere someone was making sure the world was still going about its business.
Since then, the sound of a train drawing attention to itself with a horn, whistle or any other manually-operated contraption, has always won favours with my heart. It must be to do with the way it humanises what is superficially rather an inhuman, unthinking, uncaring contraption. A train is a beast of a thing. A train that can make musical noises is a beauty.
On the Underground, the whistle plays dependable descant to the ever-modulating harmonies of the network. While the grumbling and clanking and hissing and howling forms a kind of desolate ostinato, sailing above it all comes this plaintive clarion call. It’s both nostalgic and necessary. For besides triggering memories of past times, be they half-asleep bedroom epiphanies or half-awake cinematic escapades, the whistle helps give the Underground one of its greatest endearments: its soul.