• Military convoy to remove police car from Salisbury Hospital 
• Scotland Yard urges public ‘do not be alarmed’ by military presence  
• Sergei Skripal ‘engaging and conversing’ though still in a ‘serious’ condition
• Skripal’s daughter Yulia remains in critical, but stable condition in intensive care
• Home Secretary visits policeman hospitalised after assisting the Skripals
• New theory pair may have been poisoned at their home 

A huge military convoy of more than a dozen vehicles has arrived on the streets of Salisbury as the investigation into how a former Russian double agent and his daughter came to be poisoned with a nerve agent enters a new phase.

Army lorries, unmarked white vans, police motorbikes and ambulances drove down to a ramp leading to the entrance to the A&E unit at Salisbury District Hospital on Friday afternoon.

The purpose of the operation is understood to be to remove a police car, which has been parked outside the A&E unit, behind a police cordon. One bystander said: “It’s mad.”

Around 180 troops, including Royal Marines, RAF and chemical specialists have been brought in to assist the probe.

In a statement, Scotland Yard said: “The Counter Terrorism Policing Network has requested assistance from the military to remove a number of vehicles and objects from the scene in Salisbury town centre as they have the necessary capability and expertise. The public should not be alarmed and the public health advice remains the same.

“We have the right people with the right skills to assist with this crucial inquiry. This is a dreadful incident and my thoughts remain with the victims and their families.”

“The military has the expertise and capability to respond to a range of contingencies. The Ministry of Defence regularly assists the emergency services and local authorities in the UK. Military assistance will continue as necessary during this investigation.”

The BBC’s Daniel Sandford said the military personnel were “experts in chemical, biological, radiological and nuclear warfare.” Sky News reports there are 18 military vehicles attending in total. 

Defence Secretary Gavin Williamson said: “Our armed forces have stepped up to support the police in their investigation in Salisbury, building on the vital expertise and information already provided by our world-renowned scientists from the Defence Science and Technology Laboratory at Porton Down.”

Meanwhile, fire officers in hazmat suits were seen pinning a blue forensic tent over the memorial of Skripal’s son Alexander in Salisbury’s London Road cemetery.

Other officers in white suits and gas masks were seen packing items from the cemetery into a yellow barrel. 

It comes amid news that Sergei Skripal is in a “very serious” condition but is “conversing and engaging” after the nerve agent attack, Home Secretary Amber Rudd confirmed.

In a statement, Lorna Wilkinson, director of nursing at Salisbury NHS Foundation Trust, added: “A man in his 60s and a women in her 30s remain in a critical, but stable condition in intensive care after being exposed to a nerve agent. The police officer, who was also part of the initial response, is conscious in a serious but stable condition.”

Speaking during a visit to the city where the former Russian double agent, 66, and his daughter, Yulia, were found slumped on a park bench, Rudd described the attack as “outrageous”.

The Home Secretary offered no further details about the nerve agent, who may have used it, or how it was administered to the pair.

“I understand people’s curiosity about all those questions, wanting to have answers and there will be a time to have those answers,” Rudd said. 

Detective Sergeant Nick Bailey was on Thursday named as the police officer who was first on the scene in Salisbury, who was put into intensive care and remains in a serious but stable condition and is now sitting and talking. He was visited by Rudd during her visit to Salisbury District Hospital. 

Acting Chief Constable of Wiltshire Police, Kier Pritchard, who also visited DS Bailey at Salisbury District Hospital, said the officer was “well-loved”.

Pritchard updated the total number of people being treated as a result of the poisoning, confirming 21 people in total had been affected.

A Sky News source claimed police are now working on the theory the Skripals may have been poisoned at their home. The pair had been found on Sunday close to a Zizzi restaurant, where they had dined earlier that evening. 

On Friday, the former Metropolitan Police commissioner Lord Blair backed calls made by Labour chairwoman of the Commons Home Affairs Committee Yvette Cooper, who said the government should investigate 14 other suspicious deaths on UK soil. 

Speaking to the BBC, Lord Blair said: “I am certainly of a view that this extraordinary attack in Salisbury is … as Yvette Cooper has said, let’s have a good look at this again and see whether there is some pattern here of people who go out jogging and fall dead, and who are found dead in their house in Surrey, and so on.

“There has got to be something here that at least is worth looking at.”

Speaking later Rudd added that the government would “wait until we’re absolutely clear what the consequences could be and what the actual source of this nerve agent has been” before deciding how to respond to the incident. 

A Downing Street spokesman declined to comment on what sanctions might be taken against Russia if it was shown to be responsible for the Salisbury attack.

The spokesman said: “As both the Prime Minister and Home Secretary have said, if a state actor is found to be responsible, there will be an appropriate response.

“But the investigation by the police and authorities to establish the full facts is ongoing.

“We will take any necessary actions, but we need to ensure the police have the space to carry out the investigation.”

Defence minister Tobias Ellwood said: “Some big questions arise as to how do you stand up to a clandestine and sinister attack deliberately done to play havoc in our society?” 

He added that with Russia we are “seeing a nation interfere with elections, interfere in the Middle East and erode the international rules-based order that has provided relative peace in Europe for the last few decades.” 

Russia has denied any involvement in the incident and has accused the press of publishing anti-Russian rhetoric. The Russian embassy tweeted: “Investigation of Sergei Skripal case follows the Litvinenko script: most info to be classified, Russia to get no access to investigation files and no opportunity to assess its credibility.”

A British public inquiry found the killing of Alexander Litvinenko had probably been approved by Russian President Vladimir Putin and carried out by two Russians, Dmitry Kovtun and Andrei Lugovoy. Lugovoy is a former KGB bodyguard who later became a member of the Russian parliament.

Both denied responsibility and Russia has refused to extradite them.

The Home Secretary’s visit to Salisbury came after a flurry of activity at key sites related to the case in the city on Thursday evening. Police sealed off the gravestone of Skripal’s wife Liudmila, who was buried in 2012, and the memorial stone of his son, Alexander, who was cremated last year.