A rotary servo valve for controlling fluid flow, the servo valve comprising: a first housing portion defining a cylindrical cavity and a first layer of ports, the first layer of ports having only three pairs of ports, being a first pair of first service ports, a pair of pressure ports and a pair of return ports, the ports of each pair being arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the first layer being located at substantially the same axial position along the length of the cavity; and a first spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein the first spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius of the first spool portion blocks at least one port of the first layer so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each first service port of the first pair of the first layer and a corresponding one of the remaining ports of the first layer, each fluid flow path being defined at least in part by one of the indented sides of the first spool portion; a second housing portion defining a cylindrical cavity and a second layer of ports, the second layer having only three pairs of ports being a pair of pressure ports, a pair of return ports and a second pair of service ports being either a pair of first service ports or a pair of second service ports; the ports of each pair arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the second layer being located at substantially the same axial position along the length of the cavity; and a second spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein the second spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius of the second spool portion blocks at least one port of the second layer so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each service port of the second pair of the second layer and a corresponding one of the remaining ports of the second layer, each fluid flow path being defined at least in part by one of the indented sides of the second spool portion. a first housing portion defining a cylindrical cavity and a first layer of ports, the first layer of ports having only three pairs of ports, being a first pair of first service ports, a pair of pressure ports and a pair of return ports, the ports of each pair being arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the first layer being located at substantially the same axial position along the length of the cavity; and a first spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein the first spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius of the first spool portion blocks at least one port of the first layer so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each first service port of the first pair of the first layer and a corresponding one of the remaining ports of the first layer, each fluid flow path being defined at least in part by one of the indented sides of the first spool portion; a second housing portion defining a cylindrical cavity and a second layer of ports, the second layer having only three pairs of ports being a pair of pressure ports, a pair of return ports and a second pair of service ports being either a pair of first service ports or a pair of second service ports; the ports of each pair arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the second layer being located at substantially the same axial position along the length of the cavity; and a second spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein the second spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius of the second spool portion blocks at least one port of the second layer so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each service port of the second pair of the second layer and a corresponding one of the remaining ports of the second layer, each fluid flow path being defined at least in part by one of the indented sides of the second spool portion.