Runners taking part in the first Hertfordshire Half Marathon at Knebworth House this morning have urged organisers to delay the start after sitting in traffic on the A1(M) for up to an hour.

The Comet: The Hertfordshire Half Marathon route.The Hertfordshire Half Marathon route. (Image: Archant)

Traffic has been backing up as motorists attempt to get off at Junction 7 for Stevenage and head into Knebworth Park.

The 13.1-mile race is due to start at 9.30am.

Posting on the event page, one runner wrote: “Can’t get there as traffic is ridiculous getting in. A lot of runners like me missing the start. It’s a shambles.”

Another commented they had been stuck at the junction since 8am, and one poster from Stevenage said: “Traffic is horrendous. Hope they delay the start.”

The half marathon is run on closed roads, with the following affected: Park Lane, The Green, Hitchin Lane, London Road (B656), Village Street, Langley Lane, Three Houses Lane, Driver’s End Lane, and Old Knebworth Lane.

Roads will be reopened as runners progress, with organisers expecting all roads to be open by 12.30pm.

For more information see www.hertshalf.com/impacted-road-info-for-residents.