The son of Beeston Long, a West India Merchant and deputy Governor of the Royal Exchange Assurance Corporation, and brother of Samuel Long and Charles Long, 1st Baron Farnborough, Long married in 1786 Frances Louisa, eldest daughter of Sir Richard Neave, 1st Baronet.
He was a Vice-president of the London Institution and leader of a group of merchants and speculators who, in a private venture, undertook the construction of the docks at Wapping. The London Docks Company had a 21-year monopoly to unload all vessels entering the port with tobacco, rice, wine and brandy (except from the East and West Indies). Long and the other directors sat in the London Dock House, in New Bank Buildings, from where they oversaw their lucrative trade.
