Umbilical

1. An umbilical for use in offshore production of hydrocarbons, the umbilical comprising an exterior sheath and an assembly of functional elements positioned inside the exterior sheath, wherein at least one functional element of the assembly of functional elements comprises:

a metallic tube formed from a rigid or substantially rigid material; and

an electrical cable enclosed within the tube, said tube being tight fitting and thus applying a radial compressive force on at least a majority of a circumference of the electrical cable along a circumferential region thereof, the tube supporting a weight of the electrical cable in an axial direction,

wherein said tube is substantially watertight to maintain a dry environment around the cable.

2. An umbilical as claimed in claim 1 , wherein said tube applies said compressive force on the cable along wholly or substantially an entire length of the cable.

3. An umbilical as claimed in claim 1 , wherein said tube is a non-ferrous metal tube.

4. The umbilical as claimed in claim 3 , wherein the tube is a composite material tube comprising glass fibers.

5. An umbilical as claimed in claim 1 , wherein said tube comprises a steel tube.

6. An umbilical as claimed in claim 1 , wherein said tube is wholly or substantially impervious to the diffusion of gas, in particular hydrogen, therethrough.

7. An umbilical as claimed in claim 1 , wherein the cable comprises a single core power cable.

8. An umbilical as claimed in claim 1 , wherein the cable comprises a multi-core cable, such as a signal cable.

9. The umbilical as claimed in claim 8 , wherein the multi-core cable is a signal cable comprising a bundle of individual conductors.

10. An umbilical as claimed in claim 1 , wherein a filler material is provided between the cable and the tube.

11. The umbilical as claimed in claim 1 , wherein the tube is a non-ferrous metal tube made of high strength aluminum.

12. The umbilical as claimed in claim 1 , wherein the tube is a non-ferrous metal tube made of copper alloys.

13. The umbilical as claimed in claim 1 , wherein the tube is a composite material tube comprising carbon fibers.

14. The umbilical as claimed in claim 1 , wherein the tube is a composite material tube comprising aramid fibers.

15. An umbilical as claimed in claim 1 , wherein said tube is a tube made of a combination of metal and a composite material.

16. An umbilical as claimed in claim 1 , wherein said electrical cable comprises at least one copper conductor.