I could be wrong, but I believe that the decision to disperse PQ17 was made by the Admiralty (Admiral Sir Dudley Pound, to be specific) and communicated to the Escort as a direct order. There are a number of accounts of this debacle, but for a seaman's eye view try a book called "Hearts of Oak" by Tristan Jones. According to Jones, who served on one of the "O" class destroyer escorts in PQ17, the crew came very close to mutiny when they learned of the order.