The plans showed three tunnels, at Shrewley, Rowington and Yardley, but as construction progressed, the last two became deep cuttings.

However, construction of the Grand Junction Canal, which would provide a link to London, was started at a similar time, and the committee wisely took the decision in April 1794 to increase the width of the tunnel to 16 feet (4.9 m), allowing wide barges to pass through it.

[1] The tunnel is 433 yards (396 m) long,[2] built of brick and is wide enough for two narrow boats to pass each other, although it has no towpath inside.

It officially opened on 19 December 1799 when the rest of the Warwick and Birmingham Canal was completed, although no trading took place until the following March.

The interior of the tunnel is unusually wet and this has led to the creation of flowstone formations.