Auto-injector for administering a dose of a liquid medicament, comprising an elongate housing, a syringe and a trigger button, wherein an interlock mechanism is provided for defining an operation sequence of the auto-injector in a manner to allow the trigger button to be operated only when a proximal end of the auto-injector is pressed against an injection site, wherein a detector means is arranged inside the elongate housing at the proximal end, the detector means slidable in longitudinal direction and biased by a detector spring into a position with the detector means protruding beyond the proximal end, wherein a dog (16.2) is arranged at the trigger button and wherein at least one longitudinal bar (18.1, 21) is provided, at least one of the bars slidable in longitudinal direction and coupled to the detector means for joint movement at least in distal direction, wherein a recess (21.1) for the dog (16.2) is provided in the bar for allowing the trigger button to be pressed when the detector means is being pushed into the auto-injector and wherein otherwise the dog (16.2) is engaged with the bar in a manner to prevent the trigger button from being pressed, wherein a loading bay is arranged slidable in longitudinal direction in the auto-injector in a manner to advance or retract the syringe, wherein a syringe latch arm having a distal end and a proximal end is pivoted about a latch arm axis transversally arranged to and offset from a longitudinal axis of the auto-injector, wherein the distal end of the latch arm is arranged for engaging behind a shoulder (7.1) arranged at the loading bay in a manner to prevent the loading bay from being moved in proximal direction and wherein the proximal end of the latch arm is arranged for being engaged when the detector means is pushed into the auto-injector thus disengaging the distal end of the latch arm from the shoulder (7.1), the auto-injector further comprising: - the elongate housing arranged to contain the syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the housing having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the housing, - a drive spring capable of, upon activation: - pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, and - operating the syringe to supply the dose of medicament, and - the trigger button arranged to lock the drive spring in a compressed state prior to manual operation and capable of, upon manual operation, releasing the drive spring for injection, characterised in that, at least one of the bars (18.1) comprises a dog (18.2) protruding from the bar (18.1) to engage the proximal end of the latch arm when the detector means is pushed into the auto-injector thus disengaging the distal end of the latch arm from the shoulder (7.1), and in that elongate housing comprises a distal portion (2.1) and a proximal portion (2.2) connected by a hinge, the portions (2.1, 2.2) rotatable about the hinge relative to each other between an aligned position and a maximum opening angle, wherein the drive spring may be compressed by rotating the portions (2.1, 2.2) out of the aligned position towards the maximum opening angle, wherein the trigger button is arranged to lock the drive spring in the compressed state when the portions (2.1, 2.2) are rotated at least almost to the maximum opening angle and wherein the loading bay for holding the syringe is arranged in the proximal portion (2.2), the loading bay being accessible from its distal end for loading or unloading the syringe when the portions (2.1, 2.2) are rotated out of the aligned position. - the elongate housing arranged to contain the syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the housing having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the housing, - a drive spring capable of, upon activation: - pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, and - operating the syringe to supply the dose of medicament, and - pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, and - operating the syringe to supply the dose of medicament, and - the trigger button arranged to lock the drive spring in a compressed state prior to manual operation and capable of, upon manual operation, releasing the drive spring for injection, characterised in that,