1. A method of data processing in a data processing system having a shared memory system, the method comprising: in a processing unit of the data processing system, executing a memory transaction, wherein executing the memory transaction includes: executing a plurality of transactional store instructions within the memory transaction that causes the processing unit of the data processing system to make a corresponding plurality of conditional updates to target memory blocks of the shared memory system conditioned on successful commitment of the memory transaction; following execution of the transactional store instruction, executing a transaction check instruction within the memory transaction that causes integrated circuitry within the processing unit to perform: refraining from committing the plurality of conditional updates caused by execution of the plurality of transactional store instructions to the shared memory system; determining, prior to conclusion of the memory transaction, whether all of the target memory blocks of the shared memory system were unmodified after conditionally updated by execution of the plurality of transactional store instructions; and in response to determining that at least one of the plurality of target memory blocks was modified after conditionally updated by execution of the plurality of transactional store instructions, setting the condition register to indicate a conflict for the memory transaction; executing a transactional load instruction that causes the processing unit to conditionally load a value from the shared memory system conditioned on successful commitment of the memory transaction; executing the transaction check instruction further causes the processing unit to perform: ensuring, prior to the determining, that the value has been bound to the transactional load instruction; and following execution of the transaction check instruction, executing one or more additional instructions of the memory transaction.