1. Apparatus for processing data under control of a sequence of program instructions including at least one predication instruction operable to predicate one or more subsequent program instructions to behave as predicated program instructions, said apparatus comprising: a plurality of instruction pipelines operable to decode in parallel respective program instructions from said sequence of program instructions; wherein a first instruction pipeline of said plurality of instruction pipelines is operable upon receipt of a predication instruction to at least partially decode said predication instruction and to generate a predication signal indicating that one or more subsequent program instructions should be predicated by said predication instruction; and a second instruction pipeline of said plurality of instruction pipelines is operable upon receipt of a program instruction to at least partially decode said program instruction to generate at least some control signals values to control said apparatus to execute said program instruction with predication assuming that said program instruction is predicated by a predication instruction and then, if a predication signal is not received from said first instruction pipeline to indicate that said program instruction is predicated, to modify said control signal values to control said apparatus to execute said program instruction without predication.