Britain’s Brexit negotiators have been denied water during showdown talks in Brussels as the EU sought to gain a competitive advantage over the UK, a civil servant has revealed.

The anonymous official said a lack of water available during talks may have been evidence of “unsporting tactics to get the upper hand”.

They also outlined the scale of “paranoia” within the British camp, highlighting fears of phone tapping and a ban on the wearing of smart watches to prevent leaks.

The account comes after The Telegraph revealed David Davis is carrying his Brexit documents and electronic equipment in a briefcase fitted with a Faraday cage to protect against hacking.