Restaurant giant McDonald's is facing its first ever strike in the UK as workers at two sites walk out in a dispute over pay and conditions.
Staff in Cambridge and Crayford, south-east London, voted overwhelmingly in favour of industrial action, amid concerns over working conditions and the use of zero-hour contracts.
The Bakers, Food and Allied Workers Union (BFAWU) said staff were demanding a wage of at least £10 an hour and more secure working hours.
McDonald's said those taking action represented 0.01% of its workforce, adding that the dispute was related to its internal grievance procedures.
But the union said the walkout was mainly over pay and zero hours contracts.
Ian Hodson, BFAWU national president, said: "We fully support the historic decision by these brave workers to stand up and fight back against McDonald's - a company that has let them down one too many times.
"McDonald's has had countless opportunities to resolve grievances by offering workers a fair wage and acceptable working conditions. This is a call for change.
"For far too long, workers in fast food restaurants such as McDonald's have had to deal with poor working conditions, drastic cuts to employee hours, and even bullying in the workplace - viewed by many as a punishment for joining a union."
McDonald's, which employs around 85,000 staff in the UK and one million worldwide, announced in April that workers would be offered a choice of flexible or fixed contracts with minimum guaranteed hours, saying that 86% have chosen to stay on flexible contracts.
A company spokesman said: "We can confirm that, following a ballot process, the BFAWU has indicated that a small number of our people representing less than 0.01% of our workforce are intending to strike in two of our 1,270 UK restaurants.
"As per the terms of the ballot, the dispute is solely related to our internal grievance procedures and not concerning pay or contracts.
"As announced in April this year, together with our franchisees, we are providing our people with the option of a guaranteed hour contract, and all restaurants will have these contracts in place by the end of 2017.
"McDonald's UK and its franchisees have delivered three pay rises since April 2016, this has increased the average hourly pay rate by 15%.
"We are proud of our people at McDonald's, they are at the heart of all we do and we work hard to ensure that our teams are treated fairly. Our internal processes underpin that commitment."
Around 40 workers will be on strike and will mount early morning picket lines before attending a rally in Westminster.
Labour leader Jeremy Corbyn offered support to the workers, saying: "Our party offers support and solidarity to the brave McDonald's workers, who are making history today.
"They are standing up for workers' rights by leading the first ever strike at McDonald's in the UK.
"Their demands - an end to zero hours contracts by the end of the year, union recognition and a £10 per hour minimum wage - are just and should be met."