Long was descended from the Longs of Wiltshire. In local affairs Long identified both before and during the Civil War with at least one of his Wiltshire relatives, Sir Walter Long, 1st Baronet of Whaddon who was an outspoken critic of the King. Like his cousin, he was a presbyterian and became an elder in parliament's presbyterian national church, with a later appointment to the parliamentary committee charged with settling the form of church government in England (1648). Following the end of royalist occupation, parliament's county committee in Somerset was revived in 1645, and Long was appointed as a member.