Hydraulic control system

1. A hydraulic control system for controlling an external device at a well installation, comprising:

a control module for generating electrical or optical control signals;

the well installation for location underwater, a well tree, a well, and an external device wherein the control module is located at the tree;

a control pod for receiving said control signals and controlling the external device;

a hydraulic line linking the control pod to the external device for the control thereof;

wherein the control pod is located remote from the tree at a structure and receives hydraulic fluid from a local supply located at the structure without a hydraulic line between the tree and the structure for controlling the external device.

2. A control system according to claim 1 , wherein the control signals are transmitted from the module to the pod via an electrically conductive coupling.

3. A control system according to claim 2 , wherein the control signals are transmitted from the module to the pod via a serial data link.

4. A control system according to claim 1 , wherein the control signals are transmitted from the module to the pod via optical fiber.

5. A control system according to claim 1 , wherein the control pod is linked to a plurality of the external devices by respective hydraulic lines.

6. A control system according to claim 1 , wherein the control pod contains a valve linked to the external device by the hydraulic line.

7. A control system according to claim 6 , wherein the control pod contains a directional control valve linked to the external device by the hydraulic line.

8. A control system according to claim 1 , wherein the structure comprises a manifold.

9. A control system according to claim 1 , wherein the external device is located at the structure.

10. A control system according to claim 1 , wherein the external device comprises a valve.