portions 10 and 12 shown in fig2 in an engaged position it will be seen in this engaged position that the latch fingers 70 all engage with the latch profile 40 it will be seen in this position that no hydraulic pressure has been applied to hydraulic lines and the ball valve 18 remains in a closed position in order to secure the coupling of the portions 10 and 12 it is necessary to apply hydraulic pressure to lock the latch fingers 70 in position this is achieved by applying pressure via hydraulic line 58 which forces the latching piston 74 and locking element 80 outward against the spring force once the operator is coupled to the horizontal tree as shown in fig2 the ball valve 18 can then be actuated to an open position this is achieved by applying hydraulic pressure via conduit 56 which causes fluid pressure to be applied to the landing 85 at the top of the internal sleeve 62 at position 86 as shown and this forces the sleeve 62 downwardly the sleeve 62 fingers 70 profile carrier 40 and upper ball valve seat 26 are forced down past valve cap 42 against the outer surface of the ball valve 18 this forces the ball valve element axially downwards and as described in co pending published international patent application no pct gb93 01110 the ball is moved via the.