Gamul was the son of Thomas Gamul. The family was of Buerton, Chester He entered Inner Temple in November 1622. In 1634 he became mayor of Chester. He was elected Member of Parliament for City of Chester for the Long Parliament in November 1640.
During the Civil War, Gamul was very active in the defence of Chester. In June 1643 he established a town guard, of which he was colonel, and enlisted all able-bodied men between 16 and 60. After the governor, Sir Nicholas Byron, was captured in March 1644, King Charles proposed Gamul in his place, but Gamul was rejected because he was unpopular with the citizens and opposed by other royalist leaders. Gamul was disabled from sitting in parliament on 22 January 1644, but was created in the baronet of Chester in April 1644. He was nominated as mayor in 1644 but was rejected. By April 1645 there were signs of popular antagonism towardsGamul and his Welsh soldiers, as conditions under the siege became increasingly difficult. Gamul entertained King Charles at town house in Chester and was with him on the Phoenix Tower when they watched the defeat of the Royalist army at the Battle of Rowton Heath.
After the siege was ended Gamul and other Royalists were dismissed from the town's administration in October 1646, and he was fined £940.
His baptism record from St Marys on the Hill, Chester (above) is shown below, dated September 1606:
Gamul married, as his first wife, Christian Grosvenor daughter of Sir Richard Grosvenor, 1st Baronet in 1621. They had two daughters, and his baronetcy became extinct on his death:
