After the murder of Regent Moray in January 1570, William Kirkaldy of Grange ranged himself definitely among the friends of the imprisoned queen. Defying Regent Lennox, Grange began to strengthen the fortifications of Edinburgh castle and town, of which he was captain and Provost, and now held for Mary. He forcibly released one of his supporters from imprisonment in Edinburgh's tolbooth, a step which led to an altercation with his former friend John Knox, who called him a murderer and throat-cutter. He arrested some leading burgesses on 29 April 1571. The King's party established their headquarters in Leith. The subsequent period has become known as the "Wars between Leith and Edinburgh." Kirkcaldy began to strengthen the spur fortification at the entrance of the castle, and in May built fortifications in the town, on the Royal Mile and on St Giles Kirk. In October 1571 the town council established itself in Leith, and Grange's men fortified Edinburgh by blocking the ends of streets and closes and burning houses on the outskirts of the city, such as Potterrow. The "lang siege" of Edinburgh castle began in mid-October, when Regent Mar brought artillery from Dumbarton and Stirling Castle.