A medicament delivery device comprising a first container having a delivery outlet at a front end thereof and a first stopper axially moveable in the first container, the first stopper defining and separating a first chamber and a second chamber in the first container, where the first chamber is axially forwards of the first stopper and the second chamber is axially rearwards of the first stopper. The medicament delivery device further comprising a second container having a second stopper axially moveable in the second container, the second stopper defining and separating a third chamber and a fourth chamber in the second container, where the third chamber is axially forwards of the second stopper and the fourth chamber is axially rearwards of the second stopper, and where the third chamber has a vent outlet in fluid communication with a venting chamber. The first stopper is connected to the second stopper by a tensile member such that axially forwardly movement of the first stopper causes axially forwardly movement of the second stopper due to tensioning of the tensile member. The first stopper is driveable in an axially forwardly direction, the first chamber is configured to contain medicament for delivery through the delivery outlet as the first stopper moves axially forwards, the third chamber contains a viscous fluid that enters the venting chamber via the vent outlet as the second stopper moves axially forwards, and the fourth chamber has a pressure that is substantially equal to or greater than the pressure of the venting chamber. As the first stopper is driven axially forwardly, the tensile member is tensioned and causes the second stopper to move axially forwardly and the venting of viscous fluid into the venting chamber via the vent outlet retards the axially forward movement of the second stopper and the first stopper.
