It was also possibly hinted at in a statement by Major General Kyrylo Budanov, the head of Ukrainian military intelligence, promising revenge for Russian attacks on Kyiv.

“Our response will not be delayed. Soon, everyone will see everything”, Budanov said on Monday.

The drones that were filmed flying over Moscow in multiple videos uploaded to social media bear a striking resemblance to the Ukrainian Ukrjet UJ-22 Airborne unmanned aerial vehicle.

This model of drone – originally developed as a reconnaissance and light attack drone for the Ukrainian military – has a range of 800km, according to Ukrjet, putting Moscow well within its reach from inside Ukrainian borders.

Like the Shahid, it is powered by a small petrol engine and it can carry a similar sized explosive payload.

While Ukraine has been developing numerous versions of the Iranian “Shahid 136” suicide drone, its foreign partners have also been rushing the procurement of a number of unmanned systems. These include the American Phoenix Ghost, which has been extensively used by the Ukrainian military over the past year, as well as a number of “complex” suicide drones sent by the British government.

While simple, slow-flying and relatively easy to shoot down, the unsophisticated nature of the such drones is one of their main advantages.

Easy to produce and costing relatively little in military terms, they can be cheaply and easily manufactured at scale and launched en masse in large waves.

The success of the Ukrainians’ own drone program should not come as much of a surprise, given the country’s proud aeronautical heritage and still relatively advanced industrial base, even after more than a year of war.

After all, this is the same country that gave the world the largest aircraft to have ever flown, the Antonov An-225 Mriya.

The Russian government was also clearly aware of the possibility of such a system being used to attack targets in Moscow and elsewhere inside Russia.

Over the past few months, Russian air defence systems have been redeployed to protect strategically and symbolically important targets within the country.

In one highly publicised example, in January a Pantsir S1 short-range air defence system was placed on the roof of the Russian defence system in the heart of Moscow.

The specific employment of the Pantsir, a system designed to engage threats at short range, was a good indication of the threat the Russian military expected to face – incoming drones.

For the Russians, the advent of the Ukrainian Shahid will present a number of immediate problems.

Firstly, the penetration of Moscow’s air defences is acutely embarrassing for the government, demonstrating its inability to protect the capital from the suspected Ukrainian incursion.

President Vladimir Putin sought to dispel the fears of citizens but his reference to similar problems with air defences at a Russian-controlled Hmeimim airbase in Syria would hardly have calmed nerves. The Russian capital is not some little-known military installation in a far-off country.

Loading

Aside from the obvious symbolic effect, the drone raid may also have strategic impact in forcing the Russian military to redeploy further air defence assets to protect key locations within Russia from any further Ukrainian drone strikes.

Here, Russia’s sheer size works against it. There are numerous strategic sites spread over a huge amount of territory.

Putin’s billionaire friends, many of whom live in the wealthy neighbourhoods hit in Tuesday’s strikes on Moscow, could also now pressure him to do more to protect the city.

For the Ukrainians, any redeployment of Russian air defence systems away from the front line brings obvious benefits at a potentially crucial time in the war, just before the launch of their long-touted counter-offensive.

The Telegraph, London

Get a note directly from our foreign correspondents on what’s making headlines around the world. Sign up for the weekly What in the World newsletter here.