An assembly method comprising: providing a digital model of at least part of an aircraft airframe, the digital model of the at least part of the aircraft airframe comprising a respective digital model of each of a plurality of component parts of the aircraft airframe; providing the plurality of component parts of the aircraft airframe, each of the plurality of component parts comprising one or more predrilled fastener holes; wherein: the step of providing the plurality of component parts of the aircraft airframe comprises, for each of the plurality of component parts: providing a workpiece comprising a plurality of attachment features for attaching the workpiece to a machining fixture; attaching, using the attachment features, the workpiece to the machining fixture; determining a datum, the datum being dependent upon the relative positions of the attachment features; providing a first digital model of that component part; controlling machining apparatus with respect to the datum to machine the workpiece attached to the machining fixture so as to produce that component part as specified by the first digital model; and wherein the assembly method further comprises: fixing a first component part to a support structure; fixing a second component part to an end effector of a robot arm; and wherein: the first component part is fixed to the support structure using the attachment features of the first component; and/or the second component part is fixed to the end effector using the attachment features of the second component and wherein the assembly method further comprises: using the digital model of the at least part of the aircraft airframe, controlling the robot arm to move the second component part relative to the first component part thereby moving the second component part into a position relative to the first component part specified in the digital model of the at least part of the aircraft airframe, and causing one or more predrilled holes in the second component part to align with one or more predrilled holes in the first component part respectively; and attaching the second component part to the first component part by inserting a respective fastener through each pair of the aligned predrilled holes, thereby producing an assembled at least part of the aircraft airframe. providing a digital model of at least part of an aircraft airframe, the digital model of the at least part of the aircraft airframe comprising a respective digital model of each of a plurality of component parts of the aircraft airframe; providing the plurality of component parts of the aircraft airframe, each of the plurality of component parts comprising one or more predrilled fastener holes; wherein: the step of providing the plurality of component parts of the aircraft airframe comprises, for each of the plurality of component parts: providing a workpiece comprising a plurality of attachment features for attaching the workpiece to a machining fixture; attaching, using the attachment features, the workpiece to the machining fixture; determining a datum, the datum being dependent upon the relative positions of the attachment features; providing a first digital model of that component part; controlling machining apparatus with respect to the datum to machine the workpiece attached to the machining fixture so as to produce that component part as specified by the first digital model; and wherein the assembly method further comprises: providing a workpiece comprising a plurality of attachment features for attaching the workpiece to a machining fixture; attaching, using the attachment features, the workpiece to the machining fixture; determining a datum, the datum being dependent upon the relative positions of the attachment features; providing a first digital model of that component part; controlling machining apparatus with respect to the datum to machine the workpiece attached to the machining fixture so as to produce that component part as specified by the first digital model; and wherein the assembly method further comprises: fixing a first component part to a support structure; fixing a second component part to an end effector of a robot arm; and wherein: the first component part is fixed to the support structure using the attachment features of the first component; and/or the second component part is fixed to the end effector using the attachment features of the second component and wherein the assembly method further comprises: using the digital model of the at least part of the aircraft airframe, controlling the robot arm to move the second component part relative to the first component part thereby moving the second component part into a position relative to the first component part specified in the digital model of the at least part of the aircraft airframe, and causing one or more predrilled holes in the second component part to align with one or more predrilled holes in the first component part respectively; and attaching the second component part to the first component part by inserting a respective fastener through each pair of the aligned predrilled holes, thereby producing an assembled at least part of the aircraft airframe.