When a data processing operation requires data that is stored in a first cache and the fetching of the data into the first cache is dependent upon data stored in another cache, and an attempt to read the data from the first cache “misses”, the data processing operation is added to a record of data processing operations that have missed in the first cache and the data that is required for the data processing operation is fetched into the first cache by reading the data that is required to fetch the data into the first cache from the another cache and then using that data from the another cache to fetch the required data into the first cache. When the data that is required for the data processing operation has been fetched into the first cache, the data processing operation is performed using the fetched data.