It is smaller than your fingernail, but this hairy beetle is one of the biggest single threats to the UK's forests.

The bark beetle has been the scourge of Europe, killing millions of spruce trees, yet the government thought it could halt its spread to the UK by checking imported wood products at ports.

But this was not their entry route of choice - they were being carried on winds straight over the English Channel.

Now, UK government scientists have been fighting back, with an unusual arsenal including sniffer dogs, drones and nuclear waste models.

They claim the UK has eradicated the beetle from at risk areas in the east and south east. But climate change could make the job even harder in the future.