1. A method comprising: receiving a handwritten input character string having an unrecognized character; determining at least one character sub-string preceding the unrecognized character in the input character string; providing, by means of handwriting recognition, one or more candidate characters for the unrecognized character; identifying, amongst stored character strings, one or more character strings comprising an initial character sub-string identical to the determined character sub-string; and selecting, based on the identified one or more character strings, one of the one or more candidate characters that is most likely to be a correct recognition of the unrecognized character, wherein if a complete character string preceding the unrecognized character in the input character string is not identical to any stored character string or an initial sub-string of any stored character string, determining at least one character sub-string comprises: identifying any initial character sub-string of the input character string preceding the unrecognized character, which is identical to one of the stored character strings or to an initial character sub-string of one or more of the stored character strings, and which together with a succeeding character is not identical to any one of the stored character strings or to an initial character sub-string of any one of the stored character strings; and determining a character sub-string consisting of a terminal character sub-string of the input character string preceding the unrecognized character and succeeding any identified initial character sub-string; else determining at least one character sub-string comprises: determining a character sub-string consisting of said complete character string preceding the unrecognized character in the input character string.