and other countries. The most potent of the novichok substances are considered to be more lethal than VX, the most deadly of the familiar nerve agents, which include sarin, tabun and soman. Novichok agents work in a similar way, by massively over-stimulating muscles and glands. Treatment for novichok exposure would be the same as for other nerve agents, namely with atropine, diazepam and potentially drugs called oximes. The chemical structures of novichok agents were made public in 2008 by Vil Mirzayanov, a former Russian scientist living in the US, but the structures have never been publicly confirmed. It is thought they can be made in different forms, including as a dust aerosol. The novichoks are known as binary agents because they only become lethal after mixing two otherwisethe death of Sturgess. Military personnel wearing gloves and gas masks were seen wrapping a white Audi in plastic, loading it on to a lorry and taking it away.

The car is believed to belong to a paramedic who attended Rowley’s address when he and Sturgess collapsed. It is understood that the paramedic is fit and healthy.

The couple became ill on 30 June at Rowley’s home in Amesbury, 32 miles (51km) south of Swindon. Police opened a murder investigation after Sturgess died in hospital on Sunday night.

The Audi is at least the third vehicle to have been seized since then. On Sunday night, service personnel wearing protective gloves and breathing apparatus towed a red van away from a road in Durrington, near Amesbury. It is thought Rowley travelled in