Abstract: A valve of the double block and bleed type construction comprises a first valve assembly housing a first ball valve and a second valve assembly housing a second ball valve. The first and second ball valves are independently actuable between open and closed positions. Each of the ball valves are held within the particular valve assembly by an annular retainer component. Each valve assembly has a passage through which fluid can pass when the ball valve is in an open condition and also a mating surface which is brought to bear against the mating surface of the other valve assembly to form a valve with a single joint.