Thieves drilled into an underground Esso fuel pipeline at Marlborough resulting in a leak of approximately 150,000 litres of fuel.

Police are investigating the damage to the pipeline on the Manton Estate, owned by the family of the late multi millionaire Robert Sangster, which happened on April 2. The multi-fuel pipeline runs from Fawley in Hampshire to Seisdon in Staffordshire and is operated by Exxon Mobil.

Members of Wiltshire and Swindon Local Resilience Forum – including Wiltshire Fire and Rescue Service, Wiltshire Council, Public Health England, Wiltshire Police and South Western Ambulance Service – were involved in the incident.

Carl Barber, the fire service crew manager based in Marlborough, said the fire service was on site round the clock for 32 hours.

He said: “There was some illegal syponing of petrol; a pressurised pipe line was tapped.

“It’s extremely dangerous, that is an extremely pressurised line at times and it can be a danger. It’s not, to my knowledge, the only case but it is the only case I’m aware of in our boundaries. Nationally it has been done before.

“It was brought to our attention by the police as some was seen to be leaking and it did take 32 hours and seven appliances because our attendance was required while they isolated and dealt with the issue.”

A 500m safety cordon was put into place while the scale of the incident was being established and nearby residents were moved as a precaution.

A police spokesman said the pipeline has been depressurised by the operator, limiting further leak of product, and there is now a quantity of diesel/petrol mixture in a hole approximately 1.4m deep.

He said: "Esso is currently dealing with the spillage, and the Environment Agency is working with Public Health England to evaluate any impact to local water courses."

Charlotte Hitchmough, director of ARK, Action for the River Kennet, said: “Esso approached us about a week after the incident to identify suitable monitoring points along the river in case the fuel gets into the river so that has been our involvement.

“Esso are taking it very seriously and they have their own team of people monitoring the situation and we are confident that there is a very competent team stopping any pollution spreading.

“There is no evidence that there have been any leaks into the river which is fantastic but what ARKs role is now is to be the eyes and ears on the river.”

A spokesman for the Environment Agency said: "We are aware of the incident.

"Esso are carrying out an in depth ground investigation to target areas to remediate. We are in frequent contact with Esso and are providing technical guidance when appropriate. At present there is no impact to the River Kennet, but we continue to monitor the situation closely."

If you spot any leaks into the river call the Environment Agency Incident Line on 0800 807060.