Eight motorcyclists rode along the A1 dangerously and aggressively preventing any drivers from getting past.
Police are appealing for witnesses to the rolling road block which happened on the northbound carriageway on Friday night.
Police say the group gathered at Stirling Corner, Borehamwood, shortly before midnight, before travelling up the A1 where they were spotted driving in a "dangerous" manner.
Officers managed to get close to the group in the Hatfield Galleria tunnel and they attempted to pull the riders over, but were forced to pursue them.
The pursuit was called off at Stevenage for the safety of the public.
PC Christopher Dougherty, from the Stevenage road policing unit, said: "This incident not only caused major congestion for anyone travelling Northbound on the A1M, it also put fellow drivers in danger. This kind of driving is unacceptable, and will not be tolerated. We are treating this as a serious offence.
"We are appealing for anyone who witnessed this incident, and anyone who believes that they may have information that could assist us with our investigation, to please come forward as soon as possible.
"Specifically, we are asking for anyone that was driving in the area at the time to please review their dash cam footage. Please review your dash cam footage, and send it to us if you believe it could assist us with our investigation."
Anyone with information or footage is asked to contact PC Dougherty directly via email at christopher.dougherty@bedfordshire.pnn.police.uk or call Crimestoppers anonymously on 0800555111.
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