This also means that this line is also inaccurate:

> For convenience, they’re actually hanging from the Jubilee footbridges, one on either side of the railway.

It's not for simple convenience: you can see in the photos that it's because the footbridges are taller then the rail bridge and come a bit before it, which allows them to install the straw hanging at the correct height to warn of the constriction before someone hits the bridge itself.

i find being warned in advance a most convenient way to avoid hitting the bridge, and if the walkways are already installed in the right place to put the bales, why that's a very convenient place to put them. if the walkways were the same height as the bridge, it would not afford that convenience because then the footbridges would themselves be the obstruction you're in danger of hitting, which would be most inconvenient.