By the Treaty of Fotheringhay, Albany promised to hold Scotland under English suzerainty in return for Edward's assistance and to deliver the southern shires into English possession. With the Duke of Gloucester, afterwards King Richard III, he marched at the head of one of the largest English armies to be assembled after the Wars of Independence—20,000 men—to Berwick, which was seized (the last time it would change hands between England and Scotland) and then, with a smaller force, to Edinburgh. Meanwhile James III was seized at Lauder Bridge as he marched to face the invasion, and was imprisoned in Edinburgh Castle. It has been suggested that there was a conspiracy between Albany and a group of magnates who had been excluded from power in the 1470s, including the king's Stewart half-uncles, the earls of Atholl, Buchan and the bishop-elect of Moray, although evidence is limited. Gloucester, meanwhile, seems to have been satisfied with the seizure of Berwick, and quit Edinburgh on 11 August. At that point the 'Lauder Lords' in Edinburgh Castle emerged and began working with Albany to form a new government. By early October Albany was acting lieutenant-general of the realm, had taken the earldom of Mar, and had re-acquired his former lands and offices.
