The head of Porton Down appears to have contradicted claims by Boris Johnson about the poisoning of a former spy, Sergei Skripal.

In an interview, the foreign secretary secretary talked about the scientific analysis of the Novichok nerve agent that was used. And he seemingly confirmed that the Porton Down defence research laboratory had “no doubt” that the substance was made in Russia.

However, Porton Down’s chief executive has now said that scientists have “not identified the precise source”.

You can read FactCheck’s long read about the case here.

The analysis

Mr Johnson’s claims were made to German TV channel Deutsche Welle, while reiterating the British government’s allegations against Russia.

The interviewer asked him: “You argue that the source of this nerve agent, Novichok, is Russia. How did you manage to find it out so quickly? Does Britain possess samples of it?”

During the course of a long response, Mr Johnson appeared to suggest that scientists from the UK’s military laboratory were adamant that the Novichok was Russian-made.

He said: “I genuinely think Russia is an incredible country, a fantastic place, and it pains me to see the way things have got between us. So, I’m genuinely distressed by what has happened. But when I look at the evidence; I mean, the people from Porton Down, the laboratory…”

“They have the samples?” the interviewer interjected.

“They do,” replied Mr Johnson. “They do. And they were absolutely categorical and I asked the guy myself, I said, ‘Are you sure?’ And he said there’s no doubt.”

Mr Johnson’s comments do not appear to match with further remarks by the head of Porton Down himself.

Speaking yesterday, Gary Aitkenhead said: “We were able to identify it as Novichok, to identify that it was military-grade nerve agent.”

But he added: “We have not identified the precise source, but we have provided the scientific info to government who have then used a number of other sources to piece together the conclusions you have come to.”

Aitkenhead said that identifying the source would require “other inputs”, explaining: “It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured.”

The apparent contradiction has already been leapt on by Labour. Shadow home secretary, Diane Abbott, said: “I don’t understand where he got that information from.”

And Labour MP Chris Williamson said: “Boris Johnson is your Foreign Secretary and he just lied to justify our country’s foreign policy.”

Meanwhile, Sky News quotes an unnamed source in the Foreign Office who said Mr Johnson “misspoke”.

But this is not the only time the government has made this claim. The Russian embassy in London has highlighted a tweet by the Foreign Office last month. The tweet said that Porton Down had “made clear” that the Novichok nerve agent was “produced in Russia”.

The tweet has now been deleted, with the Foreign Office explaining that it had been “truncated and did not accurately report our Ambassador’s words”.

In a statement today, the Foreign Office backed Mr Johnson’s remarks by suggesting he had simply been referring to the identification of the nerve agent itself – rather than its source.

A spokesperson told FactCheck today: “The Foreign Secretary was making clear that Porton Down were sure it was a Novichok – a point they have reinforced.  He goes on in the same interview to make clear why based on that information, additional intelligence and the lack of alternative explanation from the Russians, we have reached the conclusion we have.

“What the Foreign Secretary said then, and what Porton Down have said recently, is fully consistent with what we have said throughout. It is Russia that is putting forward multiple versions of events and obfuscating the truth.”

The Foreign Office had previously explained: “This is only one part of the intelligence picture. As the Prime Minister has set out in a number of statements to the Commons since 12 March, this includes our knowledge that within the last decade, Russia has investigated ways of delivering nerve agents probably for assassination – and as part of this programme has produced and stockpiled small quantities of Novichoks; Russia’s record of conducting state-sponsored assassinations; and our assessment that Russia views former intelligence officers as targets.”

What should we read into it all?

Gary Aitkenhead’s comment may be seen as undermining the government’s allegations against Russia.

However, it is worth noting that the government has always maintained that it’s case is multi-faceted. Chemistry is only part of the story.

Professor Alastair Hay told us: “My reading is that Gary Aitkenhead was simply reaffirming what Porton had said previously about the identity of the agent. He was making sure that the laboratory’s role is clear. He pointed out the UK Government was using other intelligence evidence it had to point the finger of blame at Russia.

“But I think it is good that Aitkenhead did the reaffirmation. It keeps Porton above the fray and recognised for its scientific ability.

“Unless Porton had had a prior sample from the facility where the Novichok was made it would have been difficult to identify the source. If the environmental samples had had other ingredients from the production process in them this could have helped identify how it was made and thus help to narrow down facilities. But in the absence of that prior sample pointing a finger would be unsound.”

Professor Andrea Sella told FactCheck: “This is only partly about the chemistry… It strikes me that the Russian government is doing everything it can to cast doubt on everything. They’ve repeatedly undermined Porton Down, for example by suggesting that it might have actually made and delivered the agent. Now they leap on this statement which is very clear and very simple – the chemistry is Novichok; there is additional information from other sources that corroborates the idea that the stuff came from Russia. The demands from the Russians that the UK share its information are a transparent attempt to get the UK to reveal its intelligence information.”

“Let’s face it, there is no plausible alternative scenario. It’s about the wider pattern – over and over inconvenient Russians have been bumped off, in the UK and elsewhere. Their behaviour fits with a long standing bait and switch pattern to confuse and obfuscate.”

The verdict

We have no way of verifying what Porton Down scientists may have told Boris Johnson behind closed doors; nor do we know what he was intending to refer to in his comments.

However, the question put by the interviewer specifically referred to Russia – as did Mr Johnson’s preceding comments.

Therefore, we think people might reasonably have assumed he was claiming that Porton Down had scientific evidence to show the Novichok was made in Russia – a claim that has proved to be wrong.

At best, this means his comments were sloppy and ham-fisted. At worst, they were wrong and misleading.

The statements from Porton Down do not necessarily change the government’s overall evidence base particularly. After all, we knew all along that chemistry was only part of the story.

The statements reaffirm the importance of strong intelligence. But, as of yet, the government has not elaborated on what intelligence it has – or released any of it.