medicament in the first pathway from migrating to the secondary medicament in the second pathway while also preventing the secondary medicament in the second pathway from migrating to the primary medicament in the first pathway preferably this seal valve 260 comprises a first non return valve 262 and a second non return valve 268 as such the first non return valve 262 prevents fluid transferring along the first fluid pathway 264 for example a groove in the seal valve 260 from returning back into this pathway 264 similarly the second non return valve 268 prevents fluid transferring along the second fluid pathway 266 from returning back into this pathway 266 together the first and second grooves 264 266 converge towards the non return valves 262 and 268 respectively to then provide for an output fluid path or a holding chamber 280 this holding chamber 280 is defined by an inner chamber defined by a distal end of the second inner body both the first and the second non return valves 262 268 along with a pierceable septum 270 as illustrated this pierceable septum 270 is positioned between a distal end portion of the second inner body 230 and an inner surface defined by the needle hub of the main outer body 210 the holding chamber 280.