Tunnel dug under motorway without impacting traffic

A tunnel boring machine named Mary Anning was used continuously for 32 days

A £100m water supply project has reached a key milestone after engineers completed digging a tunnel beneath a motorway – without disrupting traffic.

A remotely operated tunnel boring machine spent 32 days digging 7m (23ft) under the M3 in Hampshire as part of Southern Water's Southampton Link Main scheme.

The tunnel is one of three that will eventually connect to Southern Water's Otterbourne site near Winchester, with the aim of improving drought resilience and securing water supplies across the county.

The water firm said the tunnel - with a 1.5m (4ft 11in) diameter - was completed between 6 October and 6 November while motorists were "blissfully unaware".

This section of the water supply project was finished on 6 November

Once complete, the pipeline will run from Otterbourne Water Supply Works to Yew Hill reservoir and then south to Rownhams Water Supply Works on the outskirts of Southampton.

Terence Hedley, senior project manager, said: "It's so exciting to reach another important milestone in the development of this essential project.

"It's a key part of our plan to create new drought-proof sources of water for Hampshire and help keep the county's taps and rivers flowing."

The scheme, which began earlier this year, is expected to take about three years to finish.