1. A method of operation of a multi-slice processor, the multi-slice processor including a plurality of execution slices, wherein each execution slice comprises a history buffer, wherein the history buffer includes a plurality of entries and at least one of the entries includes transactional memory state data corresponding to a transactional memory instruction updating a transaction memory state, the method comprising: propagating a flush signal to the plurality of entries of the history buffer; responsive to the flush signal, generating, from an entry of the history buffer, the transactional memory state data; and restoring to a transactional memory state in dependence upon the transactional memory state data.