I’ve taken my cue from an erstwhile neighbour – Alfred Hitchcock was born just up the road in Leytonstone – and I’ve moved to the rear window. I’m in search of the colour purple. But instead of the lilac that coyly shows its first blush this time of year through the satin-white of the magnolia tree and the billowing chartreuse of the willow, I’m getting a Phoenician purple that would have turned Queen Elizabeth I, who banned the royal colour from her court, apoplectic.

No fictional character has been portrayed more often on stage and screen than Sherlock Holmes. Fans flock from all over the world to see the locations where he lived, worked and brought justice to Victorian London. The BBC’s Sherlock series starring Benedict Cumberbatch and Martin Freeman has only increased his popularity.