Brexit secretary David Davis is using a hi-tech Faraday briefcase to stop spies snooping on secret Brexit documents.

Davis has been photographed carrying a silver Faraday case, which keeps contents secure by blocking electromagnetic fields. This includes all wireless, cellular, GPS and wifi signals.

He has also reportedly replaced his iWatch with a Garmin watch, which has no microphone, to prevent hackers listening in on meetings, friends of Mr Davis told The DailyTelegraph.

The measures are intended to stop foreign parties obtaining valuable information on the government’s plans for exiting the European Union.

Davis previously served in the Territorial Army’s SAS regiment after leaving school and will be accustomed to such security measures.

The Faraday case is named after English scientist Michael Faraday, who in 1836 invented a shield to block electromagnetic fields.

It is one of several available security techniques for people holding vulnerable digital information.

Keeping digital devices in the fridge is one of the easiest.

Fridges’ metal structures block out the radio signals used by snoopers to hack into cameras and microphones remotely.

Details of the measures come ahead of the first full week of Brexit talks on Monday.