TROOPS were sent in yesterday to assist police investigating the nerve agent poisoning of former spy Sergei Skripal and his daughter.

Counter-terrorism police asked for military assistance to remove vehicles and objects from the centre of Salisbury, where the pair were targeted. Much of the city centre has been cordoned off amid contamination fears.

About 180 troops, including Royal Marines, the RAF and chemical specialists, are understood to have been deployed.

The Metropolitan Police said the units were called in because they had “the necessary capability and expertise”.

Home Secretary Amber Rudd has visited the city centre and the hospital where Skripal, 66, and daughter Yulia, 33, are being cared for. Rudd said they were in a “very serious” condition, five days after they were discovered slumped on a bench. Counter-terrorism police launched an attempted murder inquiry after Skripal and his daughter were exposed to a nerve agent. Russia has denied responsibility for the attack, which comes seven years after Skripal was freed as part of a spy swap with the US. He was found guilty in 2006 of giving state secrets to MI6.

Also in hospital is detective sergeant Nick Bailey, who was part of the initial response. Former Metropolitan Commissioner Lord Blair suggested on the BBC’s Today programme that the detective had visited Skripal’s home.

He said: “There obviously are some indications the officer has actually been to the house, whereas there was a doctor who looked after the patients in the open who hasn’t been affected.”

Police said 21 people had been seen for medical treatment. The figure includes members of the public and emergency staff, some of whom have had blood tests as well as support and advice.