It has marked similarities, for example, to the arson attack on a Ukrainian-linked warehouse in east London last year for which two British men were arrested.

German intelligence is also reported to be looking at the series of car rammings – several of them fatal – that occurred ahead of the recent German elections. They believe they may have been instigated by Russian intelligence in order to inflate support for the far right.

According to Russia specialists Andrei Soldatov and Irina Borogan, Russia’s intelligence agencies have become adept at using social media not just as a tool for stirring discontent and spreading conspiracies, but recruiting local criminals, poor immigrants and mentally vulnerable individuals to carry out attacks for them.

A similar modus operandi has been used by the Iranian intelligence services to recruit spies across Israel, many of whom have been arrested in recent months.

“These attacks don’t necessarily have to be violent to be effective,” they write in Foreign Affairs.

“There are indications that Russian agencies could use social media to recruit teenagers, including those belonging to post-Soviet diasporas, to spray hateful slogans on the walls of apartment buildings in neighbourhoods with a significant migrant population, threatening or humiliating locals to incite hatred against refugees from Ukraine or Syria. These attacks don’t require much preparation and may cost only a few thousand dollars. More ambitious recruits might be paid to undertake more violent actions, such as committing arson or throwing Molotov cocktails”.

The British security services will be in no doubt about the threat from Putin’s Russia. They have been on high alert ever since the killing of Alexander Litvinenko with polonium in London in 2006 and the botched assassination of the Skripals with the nerve agent Novichok in 2018.

And earlier this month a team of Russian agents were found guilty following the biggest spying investigation in Britain. The spy ring, made up of Bulgarian nationals, plotted kidnaps, disinformation campaigns, surveillance against Ukrainian troops and secret weapon trades with China from their base in Great Yarmouth. The group received orders from Moscow via Jan Marsalek, a fugitive tech boss and one of the most wanted men in Europe.

MI5 will also be aware of Russia’s most brazen recent assassination attempt in Europe: the plot to kill in the spring of last year Armin Papperger, the head of Rheinmetall, Germany’s largest arms manufacturer. The murder was thwarted by German and American intelligence, confirmed Mr Appathurai, the Nato official, in January.

The Heathrow fire could of course yet turn out to be an accident. It is well known that the country’s infrastructure is creaking and perhaps it is just a coincidence it occurred so close to the airport at such a sensitive time. Ed Miliband, the Energy Secretary, said there was “no suggestion that there is foul play” on Friday morning.

Nevertheless officers from Counter Terrorism Command were leading the investigation because of “the impact this incident has had on critical infrastructure”, The Telegraph was told. The officers – also known as ‘SO15’ – will play a key role to try to establish whether or not any hostile agents were involved in triggering the blaze.

At least 1,351 flights going to and from the airport will be impacted by the closure, with up to 291,000 passengers thought to be affected.

Inbound planes have been diverted to other airports, including Shannon in Ireland and Charles de Gaulle in Paris, with aviation experts saying the impact of disruption is “similar to 9/11”.

Terrorism or otherwise, it is likely we will see much more hybrid warfare from Mr Putin’s agents over the next few months and years.

Soldatov and Borogan say that the idea that a deal between President Donald Trump and Putin to end the fighting in Ukraine will cause Russia’s spies and saboteurs to step back is “dangerously mistaken”.

“For centuries, Russia has viewed the West as intent on Russia’s subjugation or outright destruction, and Soviet and Russian intelligence services have operated for decades on the assumption that the West is an implacable foe”, they write in Foreign Affairs this week.

“To Moscow’s spies, Trump’s courting of Putin has provided an opportunity to expand and strengthen their subversion campaign in Europe. Given the Trump administration’s scepticism toward NATO and the defence of its transatlantic allies, a US-Russian agreement could increase Moscow’s willingness to launch unconventional attacks in Europe”.

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