A valve assembly, for use in a fluid conduit, the the valve assembly comprising: a locking device (32, 132, 232) including: a plunger (36, 236) for engaging a valve in the fluid conduit, the plunger (36, 236) arranged to be moveable in a first axial direction from an undeployed position to a deployed position, the plunger (36, 236) when in its deployed position configured for holding the valve in a valve closed position; and a locking element arranged to engage the plunger (36, 236) in its deployed position so as to prevent movement of the plunger (36, 236) in a second axial direction, the second axial direction being opposite to the first axial direction, wherein the valve assembly further includes: an assembly housing (22, 24) defining a hollow bore along which flowable material may flow; and a valve moveable between a valve open position and a valve closed position, the valve when in the valve open position opening the hollow bore so as to allow flowable material to flow along the hollow bore, the valve when in the valve closed position closing the hollow bore so as to prevent flowable material from flowing along the hollow bore, wherein the plunger (36, 236) in its deployed position engages the valve so as to hold the valve in the valve closed position, wherein the valve includes a pivot portion, the pivot portion being pivotally coupled to the assembly housing (22, 24), the valve being moveable between the valve open position and the valve closed position upon pivotal movement of the pivot portion, wherein the plunger (36, 236) in its deployed position engages the pivot portion so as to hold the valve in the valve closed position. a locking device (32, 132, 232) including: a plunger (36, 236) for engaging a valve in the fluid conduit, the plunger (36, 236) arranged to be moveable in a first axial direction from an undeployed position to a deployed position, the plunger (36, 236) when in its deployed position configured for holding the valve in a valve closed position; and a locking element arranged to engage the plunger (36, 236) in its deployed position so as to prevent movement of the plunger (36, 236) in a second axial direction, the second axial direction being opposite to the first axial direction, a plunger (36, 236) for engaging a valve in the fluid conduit, the plunger (36, 236) arranged to be moveable in a first axial direction from an undeployed position to a deployed position, the plunger (36, 236) when in its deployed position configured for holding the valve in a valve closed position; and a locking element arranged to engage the plunger (36, 236) in its deployed position so as to prevent movement of the plunger (36, 236) in a second axial direction, the second axial direction being opposite to the first axial direction, wherein the valve assembly further includes: an assembly housing (22, 24) defining a hollow bore along which flowable material may flow; and a valve moveable between a valve open position and a valve closed position, the valve when in the valve open position opening the hollow bore so as to allow flowable material to flow along the hollow bore, the valve when in the valve closed position closing the hollow bore so as to prevent flowable material from flowing along the hollow bore, wherein the plunger (36, 236) in its deployed position engages the valve so as to hold the valve in the valve closed position, wherein the valve includes a pivot portion, the pivot portion being pivotally coupled to the assembly housing (22, 24), the valve being moveable between the valve open position and the valve closed position upon pivotal movement of the pivot portion, wherein the plunger (36, 236) in its deployed position engages the pivot portion so as to hold the valve in the valve closed position. an assembly housing (22, 24) defining a hollow bore along which flowable material may flow; and a valve moveable between a valve open position and a valve closed position, the valve when in the valve open position opening the hollow bore so as to allow flowable material to flow along the hollow bore, the valve when in the valve closed position closing the hollow bore so as to prevent flowable material from flowing along the hollow bore, wherein the plunger (36, 236) in its deployed position engages the valve so as to hold the valve in the valve closed position, wherein the valve includes a pivot portion, the pivot portion being pivotally coupled to the assembly housing (22, 24), the valve being moveable between the valve open position and the valve closed position upon pivotal movement of the pivot portion, wherein the plunger (36, 236) in its deployed position engages the pivot portion so as to hold the valve in the valve closed position.