A system for clustering data comprises a database for storing a plurality of data items, a clustering unit comprising components operable to receive and cluster the plurality of data items, and output clustered data items. A method of clustering data comprises receiving a plurality of data items from a database; computing distances between each pair of data items in the plurality of data items; until a stopping criterion is reached, identifying key elements, merging data items not identified as key elements with the nearest key elements, updating the computed distances; once the stopping criterion is reached, outputting cluster identities of the plurality of data items.