To onlookers at Disneyland Paris, he was just another grumpy father, dragged from queue to queue, waiting for hours to get on rides.

In reality, the grouchy dad in Minnie Mouse ears was a Russian tech boss, whose software is being used by military cadets in training to join Vladimir Putin’s killer drone force.

Major Russian defence firms and oligarchs have been sanctioned by Western governments, preventing them from travelling freely and accessing funds in Europe and America.

But a range of other Russian actors – whose work is beneficial to Putin’s war in Ukraine – are able to travel with impunity. Many technology developers appear to move without restriction.

The revelation raises serious questions about the ability of Western authorities to tackle Russian actors, even as Putin’s grey warfare on the UK and other Nato members grows bolder.