More than 150 GMB members demonstrated outside the Regent Street and New Bond Street stores to raise awareness about the proposed closure in an attempt to save the jobs of 309 workers at the factory.
GMB organiser Mervyn Burnett said: 'Burberry is as British as the changing of the guard. People buying the high-quality goods produced in Treorchy expect that they will continue to be made by skilled workers in the UK.
'The only reason for the proposed closure is that the company wants to move production to non-union workplaces overseas.'
One suggestion by the union is that the Welsh factory could produce Burberry rainwear, at a higher retail value, rather than the polo shirts that it produces at present. This would mean some redundancies, but 220 of the factory's workers would keep their jobs, according to Burnett.
The GMB intends to launch web petitions and international protests, which are understood to involve some celebrities, as part of their ongoing campaign against the fashion chain.
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