Work started on the £3m tunnels project - led by engineer Sir Owen Williams on 10 September 1962.

[4] Almost as soon as the M4 Newport bypass (junctions 24-28) had opened, the traffic levels had grown to such a degree that the road had to be widened to three lanes in each direction.

Partly due to regular tailbacks at the tunnels, a variable speed limit is in place between junctions 24 and 28.

A new M4 relief road south of Newport was proposed, but on 15 July 2009 the scheme was dropped by the National Assembly for Wales.

[6][7] There were no fatalities recorded but the closure caused a considerable amount of traffic delay in both directions of travel.