1. A method of sorting a plurality of articles (A, B, C), in which method each article has a surface provided with an indication of a routing point to which the article is to be routed, and in which method each article goes through a sorting installation in at least two passes; while a current article is passing through the installation on its first sorting pass, a digital image is generated of the surface of the article that bears said routing point's indication, said digital image of said routing point's indication is read automatically ( 4 ) so as to direct the article towards a sorting outlet of the installation accordingly, a unique image signature for the article is also extracted ( 6 ) from the digital image, and said unique image signature is recorded ( 7 ) in a database in correspondence with the digital image of the article and with the result of the reading of the routing point's indication so as for said image signature to constitute a memory access key for access to the digital image of the article and to the routing point's indication recorded in the database; and during each of the following sorting passes of each article through the installation, a current digital image of the article bearing said routing point's indication is generated again in order to extract ( 12 ) a current image signature for the article, and a match ( 13 ) is sought between said current image signature and the unique image signatures recorded in the database during the first sorting pass of the articles through the installation, so as to, when a match is detected between said current image signature and the unique image signatures, retrieve a sort code corresponding to said routing point's indication associated in the database with said unique image signature matching with said current image signature, and direct the current article to a sorting outlet of the installation accordingly to said routing point's indication; and in which method a search ( 20 ) is made in the database for at least one digital image generated during a pass in the sorting installation for at least one misrouted article in order to scrutinize the routing point's information recorded for that article in the database; said method being characterized in that, during said last sorting pass for each article through the installation, both said unique image signature and said routing point's information of said unique image signature are recorded in correspondence with said digital image of said current article in the database and with a sorting outlet storage tray to which the current article is directed so as to obtain, in a memory, various groups of digital images corresponding to respective ones of the groups of articles in the sorting outlets, and the following steps are performed for the misrouted article in order to scrutinize the information: searching ( 22 - 28 ) the database in the immediate vicinity of said digital image of said misrouted article for an article digital image that is the digital image of a reference article that is correctly routed; and scrutinizing said misrouted article starting with inputting the routing point's information of said reference article, transforming said routing point's information of said reference article into a sort code identifying the corresponding sorting outlet, retrieving all of the image signature of articles associated in the memory with the same sorting outlet, retrieving the first sorting pass and last sorting pass digital images associated with the unique image signatures found, checking that at least one of said digital images corresponds to the digital image of a reference article, and comparing said digital image of a reference article with the digital image of the misrouted article to reach a conclusion concerning the misrouting.