David Smith, 58, received a 13-year and two-month prison sentence for betraying Britain by selling classified documents to Russia.

He had used his position at the British embassy in Berlin to gather sensitive information that could have endangered people’s lives.

The Old Bailey heard that they could have ‘potentially catastrophic’ consequences for every British official in Berlin, with the cost of updating security estimated at £820,000.

Smith admitted to disliking the United Kingdom and Germany and sympathising with Russian authorities.

Smith “abused his position in the British embassy in Berlin to covertly collect and pass sensitive information to the Russian state,” according to Nick Price, head of the Special Crime and Counter Terrorism Division.

“These crimes were an attack on our country and could have jeopardised national security,” he said, adding that Smith’s actions were motivated by more than just money and greed.