Finding two-word collocations is a well-studied task within natural language processing. The result of this task for a given headword is usually a list of collocations sorted by a salience score. In corpus manager Sketch Engine, these pairs are extracted from data using a word sketch grammar relation rules and log-dice statistics resulting in a sorted list of triples . The longest–commonest match is a straightforward extension of these two-word collocations into multiword expressions. The resulting expressions are also very useful for representing the most common realisation of the collocational pair and to facilitate the interpretation of the raw triplet because sometimes, for such a triple, it is not clear from what texts it comes. We present here an algorithm behind the longest–commonest match together with a simple evaluation. The longest–commonest match is already implemented in Sketch Engine.