An injection device comprising: an actuator adapted to, when actuated, cause commencement of an injection sequence, wherein the actuator comprises an engagement surface having an edge, wherein the actuator is adapted to move between a first position in which commencement of the injection sequence is prevented, and a second position in which commencement of the injection sequence occurs and wherein the actuator comprises a pivot and is configured to rotate between its first and second positions about the pivot; a drive mechanism (120,121), wherein the actuator comprises a locking surface which is adapted to inhibit the drive mechanism when the actuator is in its first position and which is further adapted not to inhibit the drive mechanism when the actuator is in its second position, a locking mechanism adapted to be moved between a locked position in which the locking mechanism prevents the actuator from being actuated, and an unlocked position in which the actuator can be actuated to cause commencement of the injection sequence, wherein the locking mechanism comprises a contact portion; wherein the contact portion comprises a protrusion which extends from the locking mechanism and terminates in a surface which in the locked position of the locking mechanism projects against the engagement surface of the actuator thereby preventing rotation of the actuator, wherein the locking mechanism is adapted such that as the locking mechanism is moved from its locked position to its unlocked position the surface moves past the edge of the engagement surface so that the curved surface of the contact portion is not in contact with the engagement surface of the actuator when the locking mechanism is in its unlocked position, wherein the engagement surface is a planar surface on a first portion which extends from the actuator, characterised by the surface of the contact portion being a curved surface and wherein the locking mechanism slides between its locked position and unlocked position along a first axis A, wherein the protrusion extends along a second axis B, the first portion extends along third axis C which is parallel to the first axis A, and wherein the second axis B and third axis C intersect each other with an intersection angle of between 45 and 90 degrees. an actuator adapted to, when actuated, cause commencement of an injection sequence, wherein the actuator comprises an engagement surface having an edge, wherein the actuator is adapted to move between a first position in which commencement of the injection sequence is prevented, and a second position in which commencement of the injection sequence occurs and wherein the actuator comprises a pivot and is configured to rotate between its first and second positions about the pivot; a drive mechanism (120,121), wherein the actuator comprises a locking surface which is adapted to inhibit the drive mechanism when the actuator is in its first position and which is further adapted not to inhibit the drive mechanism when the actuator is in its second position, a locking mechanism adapted to be moved between a locked position in which the locking mechanism prevents the actuator from being actuated, and an unlocked position in which the actuator can be actuated to cause commencement of the injection sequence, wherein the locking mechanism comprises a contact portion; wherein the contact portion comprises a protrusion which extends from the locking mechanism and terminates in a surface which in the locked position of the locking mechanism projects against the engagement surface of the actuator thereby preventing rotation of the actuator, wherein the locking mechanism is adapted such that as the locking mechanism is moved from its locked position to its unlocked position the surface moves past the edge of the engagement surface so that the curved surface of the contact portion is not in contact with the engagement surface of the actuator when the locking mechanism is in its unlocked position, wherein the engagement surface is a planar surface on a first portion which extends from the actuator, characterised by the surface of the contact portion being a curved surface and wherein the locking mechanism slides between its locked position and unlocked position along a first axis A, wherein the protrusion extends along a second axis B, the first portion extends along third axis C which is parallel to the first axis A, and wherein the second axis B and third axis C intersect each other with an intersection angle of between 45 and 90 degrees.