It was an otherwise typical day on 25 September 2021 when thousands of dead and dying crustaceans washed up on beaches in Yorkshire and the north-east of England. Early morning walkers and swimmers were aghast to find a sickening carpet of twitching, fitting crabs.

It would be the first but not the last die-off, which would see the disappearance of vast swathes of integral native sea life along an extended stretch of coast, including seal pups. It would also see the decimation of the local fishing industry and, with that, a way of life.

Environmentalists, fishers and ordinary local people wondered what could have possibly caused such a rare catastrophic incident.…