1. Data decompression apparatus arranged to act on compressed data comprising: an ordered stream of references to groups of previously decoded data items; an ordered stream of direct representations of data items to be decoded; and an ordered stream of flags indicating whether each successive decompression operation should act on a reference or a direct representation; the apparatus comprising: an output memory area; a detector to detect the number n of consecutive flags indicating that a decompression operation should act on a direct representation; and a data copier for copying to the output memory area either a next referenced group of previously decoded data or a group of n consecutive direct representations from the ordered stream of direct representations.