Two months ago, the Cordoba Foundation, a British think tank, was organising a forum in central London about political tensions in Tunisia.

But when trying to settle invoices, its efforts to pay for the event failed.

“Multiple attempts to pay the venue provider and suppliers kept declining while payments from donors into our NatWest account kept being rejected,” said Anas Altikriti, head of the group.

“All of a sudden, we realised our business accounts had been shut. There was no notice or explanation whatsoever.”