BBC reporting that, due to illegal grouse shoots, M&S cannot verify its source of grouse and so will no longer be offering grouse on its shelves. Persuaded by letter from ex RSPB's Mark Avery [edited] says M&S would otherwise be condoning criminal activity.
BBC News - Marks and Spencer takes grouse off the shelves
Here's the link to ex RSPB Mark Avery's letter A grouse with MS | Mark Avery
The letter just reeks of intimidation rather than information.