The British government has said it has enough evidence to charge two Russian men over the poisoning of Sergei and Yulia Skripal in Salisbury.

Police released images of the two men – alleged to be members of Russia’s GRU military intelligence agency – on Wednesday.

Investigators believe they travelled to Britain under the aliases Alexander Petrov and Ruslan Boshirov, and put a “novichok” nerve agent on Mr Skripal’s front door on March 4.

The Russian government has angrily denied the Theresa May’s accusation that the alleged assassination attempt “was almost certainly also approved outside the GRU at a senior level of the Russian state”.

Russian representatives have publicly questioned the truth of the British account, pointing out apparent inconsistencies in the evidence made public so far.

While it’s true to say that we don’t know everything about what happened in Salisbury on March 4, some of the points being raised by official Russian spokesmen are theories that have already been debunked.

The ‘Skripals never came home’ theory

Russia’s Permanent Representative to the United Nations, Vasily Nebenzya, aired this theory in a statement to the UN on Thursday, echoing sceptics on social media.

He said: “According to information stated by Theresa May, the suspects found themselves next to the house of Skripal approximately at noon on the 4th of March, whereas earlier in all police reports it was stated that the Skripals left their house that day early in the morning and never returned.”

It is right to say that British police think the assassins administered the nerve agent to the door at around noon. CCTV footage that puts them near Sergei Skripal’s house at 11.58am.

And it’s true that police believe the Skripals had left the house at about 9.15am that morning.

If Sergei and Yulia went out in the morning and never returned to the house, that would indeed pose a problem for investigators. How could they have come into contact with the poison?

But police have never said the Skripals went out for the whole day, and there’s good evidence to suggest they did in fact return home in the afternoon.

Within a fortnight of the incident, CCTV footage emerged showing Sergei’s maroon BMW very close to his home. The car was driving away from the house in the direction of the town centre.

FactCheck has geolocated the footage to India Avenue, just before the junction with Devizes road, seconds away from Sergei’s home on Christie Miller Road.

The footage was from a private CCTV camera at a home on India Avenue and was first published by the Daily Mirror and the Daily Mail.

Both newspapers said that the time on the camera had been set wrong and the real time was about 1.33pm.

The clear implication is that the Skripals did return home at some point, and had just left the house again in the car when these CCTV images were taken.

The time stamp on the Gatwick CCTV pictures

British police released CCTV images of the suspected poisoners arriving at Gatwick Airport two days before the incident in Salisbury.

Social media commentators quickly raised suspicions after spotting that the time stamps on both paused images are identical:

Craig Murray, a former British Ambassador who has publicly questioned the British account of the Skripal affair, tweeted and blogged about the images, saying: “Russia has developed an astonishing new technology enabling its secret agents to occupy precisely the same space at precisely the same time.”

Mr Nebenzya brought up the time stamps in his address to the UN, and Russian Foreign Ministry spokeswoman Maria Zakharova made much of it on “60 minutes”, a popular current affairs on Russian State TV.

The truth was more prosaic. After passengers clear passport control and customs at Gatwick, they are obliged to walk separately through a row of identical barriers:

The two men simply walked through two adjacent corridors, the synchronized barriers letting them in at exactly the same time.

Channel 4 News’s Chief Correspondent Alex Thomson – a frequent flyer – spotted this and confirmed with Scotland Yard that this was indeed the official explanation for the identical time stamps.

Mr Murray publicly admitted the issue was a “red herring” on Thursday morning. But later that afternoon, Mr Nebenzya was still raising it at the United Nations.

The “BZ” claim

The British government says the nerve agent used in Salisbury was a Novichok, a class of deadly nerve agent said to have been developed by the Soviet Union.

Russia denies having any Novichok programme.

Foreign minister Sergei Lavrov went a step further in April, saying traces of a completely different nerve agent had been found in samples taken from Salisbury by chemical weapons inspectors.

He said the samples contained BZ – a toxin used by NATO member states, but not Russia.

The laboratory cited by Mr Lavrov as the source of the information immediately shot him down, saying they had “no doubt” that British chemical weapons experts had correctly identified Novichok as the culprit.

The director general of the OPCW chemical weapons watchdog later confirmed that no traces of BZ had been found in samples collected in Salisbury.