This heartfelt documentary from Felipe Bustos Sierra is about the decency and moral courage of a group of Scottish Rolls-Royce workers and trade unionists. In 1974 the men downed tools, refusing to repair jet engines for the Chilean air force in protest against the bloody military coup that had toppled the government of Salvador Allende. Bob Fulton, a quick-witted shop steward, spotted that the engines were Chilean and “blacked” them, meaning that they were in dispute and couldn’t be touched. “He was a guy who was difficult for the management to handle,” a colleague chuckles.

The workers didn’t know it at the time, but the engines rusting in crates outside their factory in East Kilbride were from the planes that dropped bombs on the presidential palace a year earlier. Sierra is the son of a Chilean exile living in Belgium. He grew up in the 80s hearing the story of these mythical Scottish factory workers. Here he brings them together for a reunion over a pint and their modesty is enormously touching. In the 1970s, the unions had the power to halt work on the engines. As one of the men points out, today they would be handed a P45 and shown the door.

Tougher to watch are the interviews filmed with Chileans jailed and tortured after the coup. News of the Scottish act of solidarity reached some of the political prisoners and it gave them great strength to know they weren’t forgotten by the outside world. Sierra skilfully compiles archive footage of the coup and its aftermath, but doesn’t fully explain how strategically important it was to ground the jets. The film ends triumphantly, with the boycotters finally receiving recognition – not that they ever asked for a pat on the back. You can imagine Ken Loach directing this as drama, with Robert Carlyle or Peter Mullan as Fulton; the late Pete Postlethwaite would have been wonderful.