Boris Johnson has attempted to renew the faltering case for blaming Russia ahead of the investigation into the Skripal attack, by issuing a fundamentally new story that completely changes – and very radically strengthens – the government line on what it knows. You can see the long Foreign and Commonwealth Office Statement here.

This is the sensational new claim which all the propaganda sheets are running with:

The Foreign Secretary revealed this morning that we have information indicating that within the last decade, Russia has investigated ways of delivering nerve agents likely for assassination. And part of this programme has involved producing and stockpiling quantities of novichok. This is a violation of the Chemical Weapons Convention.

This is an astonishing claim and requires close investigation. If this information comes from MI5 or MI6, there is a process of inter-departmental clearance that has to be gone through before it can be put in the public domain – even by a Minister – which is known as “Action-on”. I have been through the process personally many times when working as head of the FCO Section of the Embargo Surveillance Centre, monitoring Iraqi arms acquisitions. It is not, unless actually at war, a Saturday night process – it would have had to have been done on Friday.

So why is this essential information being released not to Parliament on Friday, but on Andrew Marr’s sofa early on a Sunday morning, backed up with a Sunday morning official statement? This is very unusual. Furthermore, it is absolutely incompatible with what I was told last week by FCO sources – they did not know this information, and one of them certainly would have if it was based on MI6 or GCHQ reporting.

I can see only two possible explanations. One – and the most likely – depends on looking yet again extremely carefully at what the statement says. It says “we have information indicating that within the last decade”. If does not say how long we have held that information. And “within the last decade” can mean any period of time between a second and ten years ago, Very tellingly it says “within the last decade”, it does not say “for the last decade”.

“Within the last decade” is in fact the exact same semantic trick as “sale price – up to 50% off”. That can mean no more than 0.1% off and its only actual meaning is “never better than half price”.

The most likely explanation of this sentence is therefore that they have – since last week when they didn’t know this – just been given this alleged information. And not from a regular ally with whom we have an intelligence sharing agreement. It could have come from another state, or from a private source of dodgy intelligence – Orbis, for example.

The FCO are again deliberately twisting words to convey the impression that we have known for a decade, whereas in fact the statement does not say this at all.

There is a second possible explanation. MI6 officers in the field get intelligence from agents who, by and large, they pay for it. In my experience of seeing thousands of MI6 intelligence reports, a fair proportion of this “Humint” is unreliable. Graham Greene, a former MI6 officer, was writing a true picture in the brilliant “our Man in Havana”, which I cannot strongly recommend enough to you.

The intelligence received arrives in Vauxhall Cross and there is a filter. A country desk officer will assess the intelligence and see if it is worth issuing as a Report; they judge accuracy against how good access the source has and how trustworthy they are deemed to be, and whether the content squares with known facts. If passed, the intelligence then becomes a Report and is given a serial number. This is not a very good filter, because it still lets through a lot of rubbish, but it does eliminate the complete dregs. One possible source of new information that has suddenly changed the government’s state of knowledge this weekend is a search of these dregs for anything that can be cobbled together. As I have written in Murder in Samarkand, it was the deliberate removal of filters which twisted the Iraqi WMD intelligence.

In short, we should be extremely sceptical of this sudden new information that Boris Johnson has produced out of a hat. If the UK was in possession of intelligence about a secret Russian chemical weapons programme, it was not under a legal obligation to tell Andrew Marr, but it was under a legal obligation to tell the OPCW. Not only did the UK fail to do that, the UK Ambassador Sir Geoffrey Adams was last year fulsomely congratulating the OPCW on the completion of the destruction of Russia’s chemical weapons stocks, without a single hint or reservation entered that Russia may have undeclared or secret stocks.

On the Andrew Marr programme, Boris Johnson appeared to say for the first time that the nerve agent in Salisbury was actually made in Russia. But this is a major divergence from the published FCO statement, which very markedly does not say this. Boris Johnson was therefore almost certainly reverting to his reflex lying. In fact the FCO statement gives an extremely strong hint the FCO is not at all confident it was made in Russia and is seeking to widen its bases. Look at this paragraph:

Russia is the official successor state to the USSR. As such, Russia legally took responsibility for ensuring the CWC applies to all former Soviet Chemical Weapons stocks and facilities.

It does not need me to point out, that if Porton Down had identified the nerve agent as made in Russia, the FCO would not have added that paragraph. Plainly they cannot say it was made in Russia.

The Soviet Chemical Weapons programme was based in Nukus in Uzbekistan. It was the Americans who dismantled and studied it and destroyed and removed the equipment. I visited it as Ambassador to Uzbekistan shortly after they had finished – I recall it as desolate, tiled and very cold, nothing to look at really. The above paragraph seeks to hold the Russians responsible for anything that came out of Nukus, when it was the Americans who actually took it.