Brunel's south entrance lock and swing bridge

Brunel's south entrance lock and swing bridge, built between 1844 and 1849 by Isambard Kingdom Brunel, features lock and quay walls, with the swing bridge constructed from 1875 to 1876 based on an earlier design by Brunel.

The lock is made of pennant rubble and ashlar, while the bridge is constructed from steel. The lock has an inverted elliptical-arched basin with a chamfered recess and a hinge on the south side for a single-leaf wrought-iron caisson gate, which used to seal the lock, along with channels for the hand-operated chains that closed it. Currently, the lock is sealed by a concrete wall with sluice gates. The swing bridge has tubular section long members, steel sides, and a timber-floored deck. It remains fixed in its open position across the lock, and the timber deck was replaced in the 21st century.

On the Avon side of the bridge, the lock has been supported against the north chamber wall to create a platform for boat repairs, which is now overgrown as of 2023. There is a small dock set into the chamber wall on the basin side of the bridge, and some coping stones have been replaced with concrete. A modern landing stage is attached alongside the wall, and a concrete jetty at the east entrance to the lock provides a footpath across the basin.

Additionally, there is a former gas lamp standard beside the north end of the bridge, with early 20th-century railings lining a raised section of ground that aligns with the open position of Brunel’s Swing Bridge next to North Entrance Lock, which is also listed as Grade II*. The north end of this raised area is faced in rubble stone. On the north side of the lock, there is a mid-19th century capstan marked "JD Green/ Bond Iron Founder."