BBC

“…..The name Novichok means “newcomer” in Russian, and applies to a group of advanced nerve agents developed by the Soviet Union in the 1970s and 1980s.

They were known as fourth-generation chemical weapons and were developed under a Soviet programme codenamed Foliant….

These nerve agents were designed to escape detection by international inspectors…..

One of the group of chemicals known as Novichoks – A-230 – is reportedly five to eight times more toxic than VX nerve agent…..

A number of variants of A-230 have been manufactured. One of these experimental chemicals – A-232 – was reportedly used by the Russian military as the basis for a chemical weapon known as Novichok-5.

Russia’s ambassador to the UK, Alexander Yakovenko, has suggested British authorities have identified the variant used in the Skripal attack as A-23…..

“Based on public sources, A-234 is one of the Novichok family of agents… Little is known about it but the symptoms track closely with those eyewitnesses attributed to Sergei and Yulia Skripal – as do other similar nerve agents…….

While some Novichok agents are liquids, others are thought to exist in solid form. This means they could be dispersed as an ultra-fine powder.

Some of the agents are also reported to be “binary weapons“, meaning the nerve agent is typically stored as two less toxic chemical ingredients that are easier to transport, handle and store.

When these are mixed, they react to produce the active toxic agent……..

Novichoks were designed to be more toxic than other chemical weapons, so some versions would begin to take effect rapidly – in the order of 30 seconds to two minutes.

The main route of exposure is likely to be through inhalation, though they could also be absorbed through the skin.

However, in powder form an agent might take longer to cause a reaction……

Novichok agents have similar effects to other nerve agents – they act by blocking messages from the nerves to the muscles, causing a collapse of many bodily functions.

Dr Mirzayanov told BBC Russian that the first sign to look out for was miosis, the excessive constriction of the pupils.

A larger dose could cause convulsions and interrupted breathing…..”

BBC

“…..Dr Stephen Jukes, an intensive care consultant at the hospital, said: “When we first were aware this was a nerve agent, we were expecting them not to survive.

“We would try all our therapies. We would ensure the best clinical care. But all the evidence was there that they would not survive.”

Both Skripals were heavily sedated which allowed them to tolerate the intrusive medical equipment they were connected to, but also helped to protect them from brain damage, a possible consequence of nerve agent poisoning.

Over time, the sedation was reduced and the ventilation switched from the mouth to the trachea, as shown by the vivid scar seen on Yulia Skripal’s neck in the TV statement she gave after she was released.

Once the patients became more conscious, staff had to carefully consider what they could tell them without prejudicing the police investigation, and decide on the right moment to allow questioning by detectives.

Medical director Dr Christine Blanshard explained: “Those are very difficult decisions, because on the one hand you want to provide reassurance to the patients that they are safe and they are being looked after, and on the other hand you don’t want to give them information that might cause difficulties with subsequent police interviews.”

It was the doctors and nurses that, out of concern for their patients, insisted that international inspectors obtain a court order before they would be allowed to take blood samples from the Skripals.

Dr Jukes explained: “These are vulnerable patients, they needed some form of advocate and without a court order we could not allow things to happen to them without their consent.”

Once the Skripals were stable and able to speak, the key concern for medical staff was how their production of the key enzyme acetylcholinesterase – needed to re-establish their normal body functions – could be stimulated.

The body will do this naturally after nerve agent poisoning, but the process can take many months.

In trying combinations of drugs, Dr Murray says the hospital received input from “international experts”, some of them from Porton Down.

The laboratory, internationally known for its chemical weapons expertise, processed tests and offered advice on the best therapies.

New approaches to well-known treatments were tried. Dr Jukes said that the speed of the Skripals’ recovery came as a very pleasant surprise that he cannot entirely explain……”