Why is a bundle of straw suspended from Blackfriars Bridge?

As a bridge owner, City Bridge Foundation must comply with an old Thames byelaw which requires us to suspend a bundle of straw from any bridge arch with reduced headroom, as a warning to vessels using the river below.

The current bundles of straw are in place at Blackfriars Bridge because the second stage of our £17.2m renovation began in April 2026. We’re installing scaffolding so contractors can safely access the sides and underside of the bridge, which means there is less space beneath some of the spans while work is underway.

The precise wording of the byelaw, one of many overseen by the Port of London Authority, is:

In the past we have used bales of straw; this time we are using bundles. You may spot both being used on other bridges in London that cross the Thames or its tidal tributaries.

No one seems certain when this custom first began. One theory links it to the hay barges that once transported feed for the vast number of horses in London until the early 20th century. When stacked high, their cargo could easily have caught on overhead obstructions – perhaps inspiring the practice of placing visible bundles above the river. If you have a better explanation or historic images of the tradition, we’d love to hear from you.

Straw is used rather than hay because it lasts longer and is more resistant to rain and harsh weather. Hay is a nutrient-rich crop used as animal feed, while straw is the dried stalks of cereal plants such as wheat, more commonly used for animal bedding.