"formerly commanded by the famous Coll. Lockhart"
Sir William Lockhart
Colonel Sir William Lockhart
(c.1621-1675) was Oliver Cromwell's ambassador to France, where he negotiated a military alliance against Spain. He was later also appointed governor of Dunkirk.
The instructions from Cromwell to Lockhart can be found in The English Historical Review by C. H. Firth (1906).