Pillar boxes were not always red. The earliest ornate designs were painted a splendidly regal bronze, which soon gave way to sober bottle-green. It was only in the mid-1870s that they began to acquire their coat of Beefeater red, making them handily visible from a distance.

At first, the slot for dropping the letters into was in the top of the box, but after 1859, it was moved to its more reachable spot below the rim. For a while, a vertical slot was favoured, before the wide-mouthed horizontal version superseded it.

Early designs had the majesty of classical columns. They were hexagonal rather than cylindrical, and occasionally incorporated such features as fluting, or a domed top rising to a point. Only in 1879 did the first cylindrical boxes appear, the ones we have pretty much lived with ever since.

Elliptic boxes

As well as simple cylinders, the late 19th century saw the introduction of the mighty elliptic boxes, the double-yolked eggs of the pillar-box world, with separate slots for first or second class, town or country, domestic or overseas post. Districts where the volume of post is small make do with what was originally known as a lamp box, a smaller receptacle that could be fitted to a lamp-post, or set into a wall.

Not surprisingly, it took many people time to get used to posting letters in roadside boxes. In his 1860 novel, He Knew He Was Right, Trollope has a character called Miss Jemima Stanbury who "had not the faintest belief that any letter put into one of them would ever reach its destination. She could not understand why people should not walk with their letters into a respectable post-office instead of chucking them into an iron-stump, as she called it, - out in the middle of the street with nobody to look after it."

Apart from a momentary flirtation with rectangular boxes in the 1960s, the Post Office has remained loyal to the cylindrical variety. These are the ones that are recognised throughout the world. Embossed with the royal cypher EIIR, and bearing the words “Royal Mail” (it used to be just plain old “Post Office”), they stand ready to receive.

Even though personal letter-writing may be in terminal decline, and many of us pay our bills by direct debit rather than putting a cheque in the post, life would be unthinkable without the pillar box. Where else are you going to put Auntie Lily’s birthday card?