1. A data processing apparatus for executing instructions defining operations to be performed by the data processing apparatus, the instructions including at least one complex instruction defining a sequence of operations to be performed, and the data processing apparatus comprising: a plurality of execution pipelines, each execution pipeline having a plurality of pipeline stages and arranged to perform at least one associated operation; issue circuitry for interfacing with the plurality of execution pipelines and scheduling performance of the operations defined by said instructions; for said at least one complex instruction, the issue circuitry being arranged to schedule a first operation in said sequence and to issue control signals to one of the execution pipelines with which that first operation is associated, the control signals including an indication of each additional operation in the sequence; when performance of the first operation reaches a predetermined pipeline stage in said one of the execution pipelines, that predetermined pipeline stage being arranged to schedule a next operation in the sequence and to issue additional control signals to a further one of said execution pipelines with which that next operation is associated in order to cause that next operation to be performed.