Hercules was one of the British Cycle Corp/ Tube Investments, along with other brands like Phillips and Sun. The BCC bikes were the main competitor of Raleigh and its other Nottingham brands (Rudge, Humber, Robin Hood, Triumph) until TI, the parent company, took Raleigh etc over in 1960.
Check the Sturmey-Archer 3 speed hub for a date; if the wheel is original, the bike might be the same year as the hub or maybe a year or so later....