Why is there a bale of straw hanging from a London bridge?

Passers-by in London have been bemused by the sight of a bale of straw hanging from one of London’s famous bridges.

The Millenium Bridge is a steel suspension bridge for pedestrians crossing the River Thames, first opened in 2000.

In recent days, workmen were observed strapping a bale of straw and hanging it from the underside of the bridge.

Have they lost the plot? Apparently not.

There is an ancient tradition and, it has emerged, a legal requirement to hang a bundle of straw from the bridge to warn passing ships of work being undertaken on the bridge.

Workers on the Millennium Bridge, by reducing the headroom of the bridge while they work, have triggered an ancient by-law of London requiring that a bale of straw be hung underneath to warn river traffic: pic.twitter.com/dVgtf0mZU7

— Carob Mill (@carobmill) October 17, 2023

The Port of London Thames Byelaws 2012 requires a bundle of straw to be hung from all bridges, including the famous landmark Tower Bridge.

The byelaw states: “When the headroom of an arch or span of a bridge is reduced from its usual limits, but that arch or span is not closed to navigation, the person in control of the bridge must suspend from the centre of that arch or span by day a bundle of straw large enough to be conspicuous and by night a white light.”

The City Bridge Foundation took to social media to explain the hanging bale of straw, telling curious readers that it sources its straw for the job from a farm in Essex.