Bernie Sanders addressed the Durham Miniers’ Gala via videolink from the US

It is one of the golden rules observed by political speechwriters everywhere — “know your audience”.

Bernie Sanders, 76, the veteran American socialist, took an alternative approach on Saturday, using his address to Durham Miners’ Gala to claim coal is destroying the planet.

In a pre-recorded video message to the event, one of the largest trade union gatherings in Europe, Sanders called on his audience to join together to “take on the fossil fuel industry”, which he said risked “the destruction of our planet as a result of the devastating impact of climate change”.

The off-message remarks from the Vermont senator, who came second to Hillary Clinton in the race to secure the Democratic nomination for president in 2016, shocked some. First held in 1871,