Description: Inside of a greeting card - Greetings from the Royal Gunpowder Mills. "Lady of the Lea" - Explosives Barge from an original painting by Richard Penfold M.S.I.A.D. For over three centuries, explosives barges transported their awesome cargo from the Mills at Waltham Abbey to the Woolwich Arsenal and the Grand Magazines at Purfleet, via the river Lea and Thames. Road traffic across the bridges of the Lea was usually suspended as the barge passed benea th, for fear of embers (from steam driven vehicles) and other discarded means of ignition dropping onto the deck of the passing barge. Smaller craft, depicted in the illustration, were used to transport explosives materials between the various process buildings on the Royal Gunpowder Mills site, along an intricate network of narrow canals.