Bob Olley’s unsettling vision of clash between miners and police is part of 40th anniversary show in Bishop Auckland

Bob Olley was there 40 years ago at the “battle of Orgreave”. “I saw the violence,” he said, shaking his head. “I thought I was in a foreign country when I saw what the police did. It is hard to believe it happened in this country.”

The brutality he and others witnessed on 18 June 1984 as striking miners met 6,000 police officers on horses or wielding batons on foot will stay in the memory. It was in his head as, some years later, he embarked on his response to one of the world’s greatest artworks, Picasso’s Guernica.