The Bob de Moor Facebook page
includes a video dated July 2009 in which Jacques Martin
tells of how he and de Moor worked together on one of his albums.
The video is in French and here is an English translation for people interested in de Moor.
Martin begins by explaining how de Moor got involved with Herge. In 1948, E.P. Jacobs, who had done most of the background artwork on "Tintin", split from him and Herge needed to find another artist who was just as talented. The editor of "Kuifje", the Flemish version of the weekly "Tintin magazine", recommended de Moor. De Moor's early work on "Tintin" included the Moon books. Martin especially goes on about de Moor's talent in imitating the drawing of other artists, but stresses that he was not a scriptwriter. He also describes him as very nice and affable.
Martin then tells of how he was looking for a collaborator for his own series "Lefranc" which is about a reporter who travels the world fighting crooks (sounds familiar). De Moor told him that he was interested and since the Studio Herge was not doing much work at the time Herge agreed to let him work with Martin.
Martin himself went to a valley in the Swiss Alps in order to research the area where he was to set the adventure. There he heard of a local story which inspired the plot: about how the local council deceived and ruined some foreign entrepreneurs. The result was "Le Repaire du loup" ("The Wolf's Hide-Out") which is set in a Swiss valley. (As far as I know it is not available in English.)
Martin and de Moor wanted to work on more books together but this was blocked by Herge! Martin is not sure why this was since Tintin stories were only coming out every five years or so and thus Herge could have spared de Moor from time to time. He implies that it may have had something to do with him previously quitting the Studio whereas de Moor was still under contract and needed Herge's permission to work on other projects. Curiously, it seems that Herge did not stop de Moor from working on another series where his talent in imitating the work of other artists came in useful. (Martin says that it was the classic French comic "Becasine" but I cannot find any other indication that de Moor ever worked on that series.)
De Moor was "sacked" (Martin's words) from the Studio Herge in 1985, after Herge's death, and he and Martin considered working together again but then de Moor was asked to finish Jacob's uncompleted Blake and Mortimer story "Professor SatÃ³'s Three Formulae" and died soon afterwards.
Martin describes the work de Moor did on "Le Repaire du loup": Martin would draw rough sketches describing the action and then de Moor would draw the actual panels that were published. He even kept a file with detailed drawings of each of the characters in the comic. Martin suggests that this was to avoid confusion, such as drawing a scene featuring Gritz, a friendly character, when he was supposed to put in Valadin, an antagonist.
"Le Repaire du loup" was published in "Tintin magazine" in 1969-70 but was not published in book form until fours years later. Martin explains that this was partly due to him switching to a new publisher, Casterman, which also took his other series "Alix", which is set in Ancient Rome. Apparently he pitched them to Casterman along with Jacobs' "Blake and Mortimer" and Jean Graton's "Michel Vaillant".
He concludes by describing how in about 1991 he was invited to visit the Swiss valley where he set "Le Repaire du loup" and even made a couple of speeches. Apparently the locals did not bear a grudge for him exposing a local scandal.