This bridge is not as old as it looks - it was made recently in the style of the other Birmingham canal footbridges which were made by Horseley Ironworks.
The bridge links Gas Street with the Worcester Bar which separates the Worcester and Birmingham Canal from the Birmingham Canal Main Line. It was built in 1792 to prevent water being lost to the Worcester and Birmingham Canal. It reamined there for several years, during which time cargo had to be transferred across the bar to another boat. The bar was replaced with a lock in 1815 to allow boats through.
The basin used to link the 'Worcester & Birmingham Canal' to the 'Birmingham Canal Main Line'. The Worcester Bar, built in 1792, separated the two canals for 30 years so that the Birmingham Canal Navigations company didn't lose water to the Worcester & Birmingham canal.