Data processing apparatus comprises a group of two or more processing elements configured to execute processing instructions of a program task; the processing elements being configured to provide context data relating to a program task following execution of that program task by that processing element; and to receive context data, provided by that processing element or another processing element, at resumption of execution of a program task; in which a next processing element of the group to execute a program task is configured to receive a first subset of the context data from a previous processing element to execute that program task and to start to execute the program task using the first subset of the context data; and in which the next processing element is configured to receive one or more items of a second, remaining, subset of the context data during execution of the program task by that processing element.