In April 1318, Berwick-upon-Tweed, the last Scottish-claimed stronghold still in the hands of the English, was captured by Sir James Douglas and Thomas Randolph, Earl of Moray, two of King Robert Bruce's most able commanders. Ever since his defeat at Bannockburn in 1314, Edward II had been preoccupied by an ongoing political struggle with his senior barons, headed by Thomas, Earl of Lancaster. Repeated Scottish raids deep into the north of England had effectively been ignored: but the loss of Berwick was something different. Once the most important port in Scotland, it had been in English hands since 1296; during which time its defences had been greatly strengthened. News of its capture had a sobering effect on Edward and his magnates. Aymer de Valence, Earl of Pembroke, managed to arrange