1. A processing apparatus comprising: processing circuitry configured to perform processing operations in response to program instructions; a condition status storage location configured to store at least one condition flag indicating a condition of said processing circuitry; and trace circuitry configured to generate trace data elements indicative of said processing operations performed by said processing circuitry in response to said program instructions; wherein: said processing circuitry is responsive to at least one conditional instruction to perform a conditional operation in dependence on a current value of a subset of said at least one condition flag; and said trace circuitry is configured, in response to said processing circuitry processing at least one of said at least one conditional instruction, to generate a trace data element including a traced condition value indicative of at least said subset of said at least one condition flag, said traced condition value providing information for determining a processing outcome of said at least one conditional instruction, said trace circuitry is configured to store a control flag, said trace circuitry is responsive to said control flag to select whether to generate for a given program instruction said trace data element including said traced condition value, said control flag has a first state and a second state, said trace circuitry is responsive to an update of said at least one condition flag to place said control flag in said first state, and said trace circuitry is responsive to said processing circuitry processing a conditional instruction to: (a) determine whether said control flag is in said first state; and (b) if said control flag is in said first state, generate a trace data element including said traced condition value and place said control flag in said second state.