A servo valve comprising: a fluid transfer valve assembly comprising a supply port and a control port; a valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a drive means configured to move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow; wherein the drive means is arranged to rotate the spool relative to the fluid transfer assembly, the spool provided with first and second openings (71,72) arranged to selectively align with or block respective first and second flow channels (67, 68) in the fluid transfer assembly according to the direction and degree of rotation of the spool; wherein the fluid transfer valve assembly extends in a first direction between a first end and a second end and comprises a first chamber in fluid flow engagement with the supply port and, via first flow channel and first opening via the valve spool, with the control port, and a second chamber in fluid flow engagement with the supply port and a return port via the second flow channel and second opening via the valve spool; and wherein the valve spool comprises a tubular member defining a fluid chamber and extending between the first chamber and the second chamber in a direction substantially perpendicular to the first direction, such that, the first chamber is provided between the first end and the tubular member, along the first direction, and the second chamber is provided between the tubular member and the second end, along the first direction, and such that rotation of the spool is about an axis substantially perpendicular to the first direction and such that in a first position of rotation of the valve spool, the first opening aligns in the first direction with an opening from the first chamber to define a first fluid flow path from the supply port, into the first chamber and, through the first opening, into the fluid chamber, and then through the control port. a fluid transfer valve assembly comprising a supply port and a control port; a valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a drive means configured to move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow; wherein the drive means is arranged to rotate the spool relative to the fluid transfer assembly, the spool provided with first and second openings (71,72) arranged to selectively align with or block respective first and second flow channels (67, 68) in the fluid transfer assembly according to the direction and degree of rotation of the spool; wherein the fluid transfer valve assembly extends in a first direction between a first end and a second end and comprises a first chamber in fluid flow engagement with the supply port and, via first flow channel and first opening via the valve spool, with the control port, and a second chamber in fluid flow engagement with the supply port and a return port via the second flow channel and second opening via the valve spool; and wherein the valve spool comprises a tubular member defining a fluid chamber and extending between the first chamber and the second chamber in a direction substantially perpendicular to the first direction, such that, the first chamber is provided between the first end and the tubular member, along the first direction, and the second chamber is provided between the tubular member and the second end, along the first direction, and such that rotation of the spool is about an axis substantially perpendicular to the first direction and such that in a first position of rotation of the valve spool, the first opening aligns in the first direction with an opening from the first chamber to define a first fluid flow path from the supply port, into the first chamber and, through the first opening, into the fluid chamber, and then through the control port.