Dunstable

An old proverb measures plainness against a dead straight Roman road.

Watling Street runs arrow straight through Dunstable in Bedfordshire, crossing the older Icknield Way, and early modern English proverb collections use it as the yardstick for plainness. Variants include plain as Dunstable road and plain as Dunstable way; the phrase had dropped out of ordinary speech by the nineteenth century.

The plainest thing in Tudor England was the road to Dunstable.

Watling Street ran dead straight from London through the Bedfordshire town, and "as plain as Dunstable road" became a stock comparison that eventually shortened to the adjective. The road is Roman; the phrase now survives mainly in dictionaries of obsolete English.