Tailbacks on the A1(M) northbound this evening (Monday) have been caused by 'sink holes' opening up on the carriageway.

The holes are between junctions 6  - The Clock at  Welwyn - and 7 - Langley Sidings/Stevenage South.

Defects in the road's surface have been causing tailbacks on the A1(M).Defects in the road's surface have been causing tailbacks on the A1(M). (Image: BCH Road Policing Unit)

National Highways carried out urgent road surface repairs to this stretch of road in June, when a depression in the road surface required excavation and reconstruction of part of the carriageway.

In March, the same stretch of road was closed for more than a week while works were carried out to repair what National Highways called "a significant defect".

Today, the passenger of one car told this paper: "Two large sink holes have reappeared on the A1(M) north between Welwyn and Stevenage.

"These holes originally appeared in March and were supposedly repaired.

"After the rain on Sunday and Monday, two gaping holes are now causing more issues.

"The inside lane is currently closed, causing obvious delays."

National Highways has previously explained that the cause of the past defects are likely to be due to the fact that the A1(M) runs over chalk and watercourses.

Posting a photo of a hole in the road on X (formerly Twitter) this evening, the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit said: "Apologies if you are stuck in the tailback on the northbound carriageway of the A1 at Welwyn. This explains why."