Apparatus for and method of monitoring a drilling installation

An assembly comprising two tubular elements 12, 14 with primary and secondary seals 20, 22 therebetween, there being a seal cavity 24 formed between the two tubular elements 12, 14 and the primary and secondary seals 20, 22, the assembly further comprising a seal monitoring apparatus 28 comprising a housing 30 having a chamber 32 in which is located a separator 36 which divides the chamber 32 into a first sub-chamber 32a and a second sub-chamber 32b, the first sub-chamber 32a being fluidly connected to the seal cavity 24 and filled with a hydraulic fluid, the separator 36 being movable in a first direction relative to the housing 30 to increase the volume of the first sub chamber 32a and decrease the volume of the second sub- chamber 32b and in a second direction to decrease the volume of the first sub-chamber 32a and increase the volume of the second sub chamber 32b, wherein the seal monitoring apparatus 28 further includes a position sensor which is configured to generate an electrical signal which represents the position of the separator 36 relative to the housing 30.