An assembly includes two tubular elements, a primary and a secondary seal arranged between the two tubular elements, a seal cavity formed between the two tubular elements and the primary and the secondary seal, and a seal monitoring apparatus having a housing and a position sensor. The housing has a chamber enclosing a separator which divides the chamber into a first and a second sub-chamber. The first sub-chamber is fluidly connected to the seal cavity and is filled with a hydraulic fluid. The separator is movable in a first direction relative to the housing to increase a volume of the first sub-chamber and decrease a volume of the second sub-chamber, and in a second direction to decrease the volume of the first sub-chamber and increase the volume of the second sub-chamber. The position sensor generates an electrical signal which represents a position of the separator relative to the housing.