A combine harvester comprising: • a feeder at the front of the harvester, the feeder comprising a housing, an input section and an output section, • a driveline rotatably coupled to a power source of the combine and comprising a jackshaft in the vicinity of the input section of the feeder, • a combine header removably attached to a front portion of the feeder, and comprising a header driveline that includes a header drive shaft configured to be releasably coupled to the jackshaft, characterised in that the combine harvester comprises a mechanism for automatically coupling the header drive shaft to the jackshaft, said mechanism comprising: • a pendulum arm pivotably connected to the header at a first end, and arranged to pivot relative to the header, about a first pivot axis oriented transversely with respect to the jackshaft, • a bearing hub connected to the pendulum arm at a second, opposite end of the pendulum arm, the hub comprising a housing and a rotatable axle portion inside the housing and rotatable relative to the housing, wherein one end of the axle portion is rotatably connected to the header drive shaft, and an opposite end of the axle portion comprises a first part of an axial clutch, • an actuator mounted on the header and configured to actuate a pivoting motion of the pendulum arm about the first pivot axis, • a second clutch part configured to engage with the first clutch part, the second clutch part being mounted at an outer end of the jackshaft. • a feeder at the front of the harvester, the feeder comprising a housing, an input section and an output section, • a driveline rotatably coupled to a power source of the combine and comprising a jackshaft in the vicinity of the input section of the feeder, • a combine header removably attached to a front portion of the feeder, and comprising a header driveline that includes a header drive shaft configured to be releasably coupled to the jackshaft, characterised in that the combine harvester comprises a mechanism for automatically coupling the header drive shaft to the jackshaft, said mechanism comprising: • a pendulum arm pivotably connected to the header at a first end, and arranged to pivot relative to the header, about a first pivot axis oriented transversely with respect to the jackshaft, • a bearing hub connected to the pendulum arm at a second, opposite end of the pendulum arm, the hub comprising a housing and a rotatable axle portion inside the housing and rotatable relative to the housing, wherein one end of the axle portion is rotatably connected to the header drive shaft, and an opposite end of the axle portion comprises a first part of an axial clutch, • an actuator mounted on the header and configured to actuate a pivoting motion of the pendulum arm about the first pivot axis, • a second clutch part configured to engage with the first clutch part, the second clutch part being mounted at an outer end of the jackshaft. • a pendulum arm pivotably connected to the header at a first end, and arranged to pivot relative to the header, about a first pivot axis oriented transversely with respect to the jackshaft, • a bearing hub connected to the pendulum arm at a second, opposite end of the pendulum arm, the hub comprising a housing and a rotatable axle portion inside the housing and rotatable relative to the housing, wherein one end of the axle portion is rotatably connected to the header drive shaft, and an opposite end of the axle portion comprises a first part of an axial clutch, • an actuator mounted on the header and configured to actuate a pivoting motion of the pendulum arm about the first pivot axis, • a second clutch part configured to engage with the first clutch part, the second clutch part being mounted at an outer end of the jackshaft.