<p>A hydraulic system 10 provides a positive supply of hydraulic fluid at a controlled pressure to plurality of pumps. The system comprises a fluid reservoir 15 having outlet means to supply fluid to an auxiliary pump 30. A pressure chamber 16 communicates with a reservoir 15 and has outlet means to supply fluid to a plurality of working pumps 11, 12, 13. An inlet manifold 18 is provided for receiving fluid returned from the working and auxiliary pumps. <IMAGE></p>