The photo shows a side-wall of the underground quarry workings at Little Langdale Quarry in the Lake District. The rock type was worked as the local slate but is Ordovician volcaniclastic sandstone. The suturing suggests a de-watering or movement feature in the original material.
"Seathwaite Fell Sandstone Formation - Volcaniclastic-sandstone And Volcaniclastic-breccia. Sedimentary Bedrock formed approximately 451 to 461 million years ago in the Ordovician Period. Local environment previously dominated by shallow seas." BGS