Hole-in-the-wall cash machines could run out of money in the run-up to Easter after security guards voted to strike for three days next week.
Staff employed by Securicor, which delivers £1.5bn a day to banks and shops, will walkout from midnight on April 14 in a dispute over pay and crewing.
Paul Kenny, head of the GMB's London region, said: "Our members are at the end of the road from attacks on their pay and conditions - and themselves."
