IT was with a deal of understatement that the Whitehall insider admitted this week’s revelation from Porton Down was “not ideal”.

As expected, Russia is making a five-course meal of the admission by the UK Government’s own scientists that they cannot pinpoint where the Salisbury nerve agent came from. An apology is being demanded over British “idiocy”.

Yet to be fair to Theresa May she only said it was “highly likely” that, given it was Novichok, which was produced by the Soviet Union, Russia was directly or indirectly to blame. And given the Kremlin had failed to respond positively to the UK’s request for information, there was only one conclusion to make.

Plus with Moscow having form on this, the Prime Minister’s was not an unreasonable statement; which is why allies reacted in the way they did with great solidarity.

Yet Boris Johnson once again could not resist the temptation to grab headlines by leaping gung-ho over the top and declaring with Old Etonian over-confidence that the Porton Down scientists had personally told him - “absolutely categorical” - the nerve agent had emanated from Russia. Which they clearly hadn’t.

Indeed the Foreign Office has now swiftly deleted a tweet to this effect. Oh dear. One can only imagine how Vladimir Putin and Sergei Lavrov are chuckling over their vodkas in the presidential dacha.

After the Porton Down admission, the Foreign Office and No 10 were in damage-limitation mode, insisting that, of course, the scientists could not say precisely where the nerve agent had emanated from but, given “additional intelligence,” all the evidence pointed to The Kremlin.

But this was not how it was originally portrayed. No one disabused people of the clear impression given – and restated in terms by Mr Johnson – that the scientists had indeed concluded confidently that the Novichok had come from Russia.

It would have been much wiser had Whitehall said at the time that the scientific evidence plus other intelligence clearly pointed The Kremlin’s way; but it didn’t.

So now there is an enhanced ugly political row not just between London and Moscow but between Labour and the Tories.

Jeremy Corbyn accused Mr Johnson of exaggeration and having “egg on his face” while the Foreign Secretary accused the Labour leader of “playing Russia’s game”.

While some foreign allies have come out and insisted they have not changed their minds about Russian involvement, others must be scratching their heads given that around 150 Russian diplomats have been expelled.

Some might even go public at their displeasure; a Trump tweet?

In the delicate game of international diplomacy, a country is always at a big disadvantage when its chief diplomat has great difficulty in being, well, diplomatic.