Once they'd invented the postage stamp, it took 12 years for the authorities to work out that the convenient pre-payment of postage could be best exploited by the free collection of mail in secure, prominent containers.
The first pillar boxes were planted on the Channel Isles in the 1850s, and the idea is said to have come from the fertile mind of Anthony Trollope, postal surveyor and novelist.
They soon spread to the mainland (Carlisle as it happens), in 1853. There were lots of eccentric types in the Victorian era until a design by JW Penfold was adopted as the standard in 1866 (hence the name Penfold for Dangermouse's mate – the pair famously headquartered in a pillar box).
All were painted red from 1874. The only really poor design was the "Type F", of 1968, a square, modernist affair that was made from steel rather than cast iron and rusted away. Less celebrated than Giles Gilbert Scott's K6 telephone kiosk, we would miss the pillar box just as much.