Road closure on A1(M) planned after five-metre 'dip' discovered

The defect on the A1(M) was first identified on 21 March

A 5m-deep (16ft) dip has been discovered on the A1(M) in Hertfordshire.

National Highways said it took a week to determine the exact nature of the defect and work to repair it was due to begin.

The northbound stretch of the road will be closed from junctions 6, for Welwyn, and junction 7, for Stevenage, from 21:00 GMT until 06:00 on Saturday, subject to weather conditions.

Lane 2 of the southbound section will be shut from 21:00 to 06:00 on Friday.

National Highways said the closures were necessary in order to fill the 4m-wide (13ft) void and to resurface the road.

Since 21 March, 45 core-probe tests have been carried out and a design solution to rectify the defect has been finalised.

It said that while it recognised the "challenges posed" by any road closure it "condemns the unfair frustration expressed by drivers towards roadworkers".

Heather Openshaw, head of service delivery, apologised for the delays.

"I am pleased that we have now been able to determine the full extent of the defect and design the required solution ready for delivery starting on Thursday night."

Drivers have been asked to allow extra time for their journeys and to follow diversion routes.