Monday, Ed wrote about former UK spy Sergei Skripal and his daughter Yulia who were found passed out in a shopping center over the weekend. The pair were suspected to have been exposed to an unknown toxic substance and were taken to a nearby hospital. Today, the Guardian reports both father and daughter were poisoned with a nerve agent.

The former Russian spy Sergei Skripal was deliberately poisoned with a nerve agent in a case that police are now treating as attempted murder, Scotland Yard’s assistant chief commissioner has confirmed this afternoon.

Mark Rowley said the police officer who was first to the spot where the pair were found in Salisbury on Sunday afternoon was now “seriously ill” in hospital. His condition had deteriorated, Rowley said, adding: “Wiltshire police are providing support to his family.”

Describing the poisoning of Skripal and his daughter Yulia, as a major incident Rowley said that scientists had identified the toxin used. He refused to reveal the poison.

All three were suffering from “exposure to a nerve agent”. Detectives now believed that Sergei and Yulia Skripal were specifically targeted, he added, in a deliberate act. The two victims are still critically ill in hospital.

The medical and chemical evidence and the effects on the victims point to a sophisticated nerve toxin. The best known are VX and sarin.

The suspicion now is that Russian spies carried out this attempted murder as payback against a former spy. As the Guardian article points out, nerve agents are not the kind of thing you mix up in a kitchen. The precursors for these gasses are controlled substances and not easy to acquire. The nerve agent used here was mixed in a lab at considerable expense.

Skripal was convicted of spying in Russia but was released in 2010 as part of a trade that also included Russian spy Anna Chapman. Given that history, it seems Russia is most likely responsible. Russia will, of course, deny any wrongdoing, as it always does no matter how clear the evidence. But there is a precedent here.

In 2006, former FSB agent Alexander Litvinenko, who had defected to the UK, was killed with highly radioactive polonium. Before he died, Litvinenko claimed Putin was ultimately responsible for his death and a UK investigation concluded it had been a state-sponsored assassination carried out by Russia.

The remaining question is what the UK is going to do about it. UK Foreign Minister has already promised to retaliate if Russia is found responsible, but so far the only specific response mentioned has been pulling out of the World Cup (which will be held in Russia this year). The seriousness of the response will depend in part on whether anyone actually dies from the attack. At the moment, all three victims are still alive. Also, can UK scientists tie this unnamed nerve agent to Russia? For the moment, we’ll have to wait and see if they can come up with the proof.