The investigation into the Salisbury novichok attack has moved significantly forward, with security agencies and the police increasingly confident they would be able to prove a Moscow connection, following identification of those who carried out the assassination attempt.

Investigators had narrowed down the suspects around 12 days ago to between two and four people, including a woman, from CCTV footage, with two carrying and administering the nerve agent, and others providing backup. Security agencies have also made progress, they claim, in cross-checking with people who came into the country before the poisoning of former MI6 agent Sergei Skripal and his daughter Yulia last March.

A bottle found at the home of Charlie Rowley, who along with his partner Dawn Sturgess, was poisoned by the nerve agent used in the Skripal attack at the end of last month, is said to have yielded forensic evidence which has also helped drive the investigation. Ms Sturgess subsequently died on 8 July: an inquest into her death was opened and adjourned today with police enquiries continuing. Mr Rowley remains severely ill. His brother, Matthew, has said that Ms Sturgess had sprayed from a discarded perfume bottle the couple had found onto her wrist.

However, despite the advances being made in the investigation, it is unlikely any arrests will take place in this country with those responsible for the attack almost certain to have left the UK after carrying it out. All of the suspects used false identities for travel, as would be expected.

One line being pursued in the inquiry is that the attack was carried out by current or former members of the GRU, the Russian military intelligence service, where Mr Skripal had served for 15 years before “turning”. The information he provided to his British MI6 handlers, and through them to the Americans, had led to a huge number of his former comrades in the West and elsewhere being exposed.

It is believed, however, that no evidence had been found so far to prove that the attack was ordered directly by senior figures in the Kremlin, or Vladimir Putin, the Russian president. It is not known whether those involved had decided to carry out the attack autonomously or in conjunction with others, including members of organised crime gangs with security connections.

Amesbury major incident after couple exposed to novichok Show all 40 1 /40 Amesbury major incident after couple exposed to novichok Amesbury major incident after couple exposed to novichok Forensic investigators, wearing protective suits, emerge with bagged evidence from the rear of John Baker House in Salisbury, after it was confirmed that two people living in Amesbury had been poisoned with the nerve-agent Novichok. Reuters Amesbury major incident after couple exposed to novichok Dawn Sturgess, a mother-of-three from Durrington, died after being exposed to novichok Facebook Amesbury major incident after couple exposed to novichok British police are scouring sections of Salisbury and Amesbury in southwest England, searching for a container feared to be contaminated with traces of the deadly nerve agent Novichok. Reuters Amesbury major incident after couple exposed to novichok Officers hope that Charlie Rowley, whose partner Dawn died in hospital, can help them establish how the couple came to be contaminated AFP Amesbury major incident after couple exposed to novichok An investigator in a chemical suit works behind screens erected in Rollestone Street PA Amesbury major incident after couple exposed to novichok Fire and Rescue Service personel arrive with safety equipment at the site of a housing estate on Muggleton Road, after it was confirmed that two people had been poisoned with the nerve-agent novichok, in Amesbury Reuters Amesbury major incident after couple exposed to novichok Forensic investigators at John Baker House Reuters Amesbury major incident after couple exposed to novichok Police and military personnel seized a car from a quiet residential street in Swindon as part of their ongoing investigations into the nerve agent incident in Salisbury and Amesbury SWNS Amesbury major incident after couple exposed to novichok Emergency workers in military protective suits search the fenced off John Baker House AP Amesbury major incident after couple exposed to novichok A forensic investigator, wearing a protective suit, emerges from the rear of John Baker House, after it was confirmed that two people had been poisoned with the nerve-agent Novichok, in Amesbury, Britain, July 6, 2018. REUTERS/Henry Nicholls HENRY NICHOLLS Reuters Amesbury major incident after couple exposed to novichok Forensic investigators at John Baker House Reuters Amesbury major incident after couple exposed to novichok Emergency services arrive at John Baker House EPA Amesbury major incident after couple exposed to novichok Dorset Fire and Rescue Service at the house PA Amesbury major incident after couple exposed to novichok Tents set up by search teams are seen at the end of Rollestone Street, outside the John Baker House for homeless people in Salisbury. British police are scouring sections of Salisbury and Amesbury in southwest England, searching for a container feared to be contaminated with traces of the deadly nerve agent Novichok. AP Amesbury major incident after couple exposed to novichok Dorset Fire and Rescue Service at the house in Muggleton Road PA Amesbury major incident after couple exposed to novichok Fire and Rescue Service safety equipment Reuters Amesbury major incident after couple exposed to novichok Police activity at the house in Muggleton Road PA Amesbury major incident after couple exposed to novichok Emergency services arrive at John Baker House EPA Amesbury major incident after couple exposed to novichok Fire and Rescue Service safety equipment PA Amesbury major incident after couple exposed to novichok Police tents are erected outside a residential address in Amesbury, southern England, on July 6, 2018 where police reported a man and woman were found unconscious in circumstances that sparked a major incident after contact with what was later identified as the nerve agent Novichok. Police on July 6, 2018, raced to find the object that contaminated a British couple with the Soviet-made Novichok nerve agent in southwestern England where a former Russian spy was poisoned with the same toxin four months ago. / AFP PHOTO / Chris J RatcliffeCHRIS J RATCLIFFE/AFP/Getty Images CHRIS J RATCLIFFE AFP/Getty Amesbury major incident after couple exposed to novichok Emergency services arrive at the house in Muggleton Road in Amesbury PA Amesbury major incident after couple exposed to novichok Members of the emergency services at the house in Muggleton Road PA Amesbury major incident after couple exposed to novichok Gas masks AFP/Getty Amesbury major incident after couple exposed to novichok Forensic tents outside John Baker House on Rolleston Street, Salisbury, Wiltshire, where counter-terrorism police are investigating after a couple were left in a critical condition when they were exposed to the nerve agent Novichok. PRESS ASSOCIATION Photo. Picture date: Friday July 6, 2018. Dawn Sturgess, 44, and Charlie Rowley, 45, were taken ill on Saturday in Amesbury, around eight miles from where former Russian spy and his daughter were poisoned with the same substance in Salisbury in March. See PA story POLICE Amesbury. Photo credit should read: Yui Mok/PA Wire Sam Blewett PA Amesbury major incident after couple exposed to novichok Fire and Rescue Service personel prepare safety equipment Reuters Amesbury major incident after couple exposed to novichok Police investigators arrive at the site of a housing estate on Muggleton Road Reuters Amesbury major incident after couple exposed to novichok A police officer stands guard behind the housing estate REUTERS Amesbury major incident after couple exposed to novichok Police on the scene Getty Images Amesbury major incident after couple exposed to novichok The couple remain in a critical condition at Salisbury District Hospital AFP/Getty Amesbury major incident after couple exposed to novichok In March Russian former spy Sergei Skripal and his 33-year-old daughter Yulia were poisoned with the Russian-made Novichok in the town of Salisbury. British Prime Minister Theresa May has accused Russia of being behind the attack on the former spy and his daughter, expelling 23 Russian diplomats in retaliation Getty Images Amesbury major incident after couple exposed to novichok British police are cordoning off places the people are known to have visited before falling ill EPA Amesbury major incident after couple exposed to novichok British police officers stand outside a residential property in Amesbury AP Amesbury major incident after couple exposed to novichok Deputy Chief Constable of Wiltshire Police Paul Mills makes a statement to the press outside The Bowman Centre after Wiltshire Police declared the situation a major incident Getty Amesbury major incident after couple exposed to novichok Amesbury Baptist Centre PA Amesbury major incident after couple exposed to novichok Amesbury resident Sam Hobson, speaks to assembled press outside Amesbury Baptist Centre claiming to be a friend of the man and woman exposed to an unknown substance Getty Amesbury major incident after couple exposed to novichok The pair were found unconscious at an address in Muggleton Road, Amesbury Getty Amesbury major incident after couple exposed to novichok Police cordon at Queen Elizabeth Gardens in Salisbury. The town is around 10 miles from Salisbury where former Russian spy Sergei Skripal and his daughter Yulia were poisoned in a suspected nerve agent attack PA Amesbury major incident after couple exposed to novichok Deputy Chief Constable of Wiltshire Police Paul Mills makes a statement Getty Amesbury major incident after couple exposed to novichok Police officers stand outside Boots pharmacy, near to the Barcroft Medical Centre in Amesbury PA Amesbury major incident after couple exposed to novichok Amesbury Baptist Centre PA

There has been no official acknowledgement of the damage caused by Mr Skripal to Russian security by Moscow, London or Washington. But a Russian espionage analyst, Nikolai Luzan, held in a book about the Skripal case, A Devil’s Counterintelligence Dozen, that up to 300 intelligence officers were compromised.

The accusation, made by Theresa May and her ministers, most vocally by the then foreign secretary Boris Johnson, that the Skripals were the target of a state-sponsored assassination mission has been vehemently denied by Moscow.

The British government told Nato partners soon after the Salisbury attack that Yulia Skripal’s emails were hacked by Russian intelligence in 2013. It is believed that this may have been carried out by GRU and may have continued after that date. But the security agencies have refused to say whether they have any information on why the attack was carried out in March.

Amesbury couple were exposed to nerve agent novichok

The Press Association news agency reported that “investigators believe they have identified the suspected perpetrators of the novichok attack through CCTV and have cross-checked this with records of people who entered the country around that time. They [the investigators] are sure they [the suspects] are Russian.”

The progress made on identification was also confirmed by American as well as British security sources earlier this week. US intelligence agencies have been closely involved in the Salisbury investigation from the start.

Separately, the GRU agency, now known as the Main Directorate of General Staff, is the focus of an investigation by Robert Mueller, the special counsel, into Russian interference in the US presidential election, which allegedly helped to get Donald Trump to the White House. Mr Mueller’s team indicted 12 serving GRU officers last week on charges of hacking into Democratic Party computers.

Police officers search Queen Elizabeth Gardens (Reuters)

Downing Street officials had said Ms May would ask Mr Trump during the president’s visit to the UK to press the issue of the Salisbury attack with Mr Putin at his summit with the Russian president in Helsinki. US officials say they are unaware of Mr Trump raising the matter with Mr Putin.