The Duke of Hamilton (Earl of Lanark) had raised three regiments of royalist horse, which were now under his command. These, with the accessions of forces which were daily arriving from different parts of the kingdom, were quite sufficient to have put down the insurrection in the west; but instead of marching, Lanark, to everyone's surprise, proceeded through East Lothian towards the eastern borders to meet up with Sir George Munro, who was retiring upon Berwick before the army of Cromwell. The Earl of Lanark declined to attack Covenanter David Leslie, Lord Newark, acting contrary to the advice of George Munro and his other officers. According to Dr Wishart, Lanark's advanced guard, on arriving at Musselburgh, attacked some of Leslie's Covenanter outposts who defended the bridge over the River Esk, and Lanark's advanced guard, though inferior in number, immediately put them in great disorder, and killed some of them without sustaining any loss. This success was reported to the Earl of Lanark, and it was represented to him that by following it up immediately, while the enemy continued in the state of alarm, he might perhaps obtain a bloodless victory, and secure possession of the city of Edinburgh and the town of Leith. However, Edinburgh had already been taken by the Whig party in what was known as the Whiggamore Raid.