A dry powder medicament inhaler for metering an inhalation of dry powdered medicament comprising: at least one inlet and at least one outlet, wherein a communication between said at least one inlet and said at least one outlet at least comprises a mixing and deaggregation chamber and at least two dosage communications between the at least one inlet and the chamber; a dosage mechanism (104, 108) for arranging at least one dose of a medicament between the inlet and the chamber, such that said at least one dose may be delivered upon inhalation at said outlet through said communications; characterised in that the dry powder medicament inhaler further comprises: a locking mechanism wherein on moving the dosage mechanism (104, 108) from a dose collecting position to a dose administering position the locking mechanism is moved from an unlocked to a locked position preventing the metering of any further doses prior to resetting of the locking mechanism, wherein the locking mechanism comprises a locking disc and a latch wherein the latch is associated with the locking disc such that a projection from the latch in a locked position, extends through a plane of the locking disc and is aligned such that the projection abuts at least one member of the locking disc, wherein the latch comprises a tab wherein the tab is arranged such that a force on the tab moves the latch from a locked position to an unlocked position. at least one inlet and at least one outlet, wherein a communication between said at least one inlet and said at least one outlet at least comprises a mixing and deaggregation chamber and at least two dosage communications between the at least one inlet and the chamber; a dosage mechanism (104, 108) for arranging at least one dose of a medicament between the inlet and the chamber, such that said at least one dose may be delivered upon inhalation at said outlet through said communications; characterised in that the dry powder medicament inhaler further comprises: a locking mechanism wherein on moving the dosage mechanism (104, 108) from a dose collecting position to a dose administering position the locking mechanism is moved from an unlocked to a locked position preventing the metering of any further doses prior to resetting of the locking mechanism, wherein the locking mechanism comprises a locking disc and a latch wherein the latch is associated with the locking disc such that a projection from the latch in a locked position, extends through a plane of the locking disc and is aligned such that the projection abuts at least one member of the locking disc, wherein the latch comprises a tab wherein the tab is arranged such that a force on the tab moves the latch from a locked position to an unlocked position. a locking mechanism wherein on moving the dosage mechanism (104, 108) from a dose collecting position to a dose administering position the locking mechanism is moved from an unlocked to a locked position preventing the metering of any further doses prior to resetting of the locking mechanism, wherein the locking mechanism comprises a locking disc and a latch wherein the latch is associated with the locking disc such that a projection from the latch in a locked position, extends through a plane of the locking disc and is aligned such that the projection abuts at least one member of the locking disc, wherein the latch comprises a tab wherein the tab is arranged such that a force on the tab moves the latch from a locked position to an unlocked position.