You know, you said this probably wasn't a Broster book, but I think Laurent's situation here is just the sort of duty/loyalty/honour conflict that would go perfectly in a Broster book :D And, aww, I can just see Aymar smilingly confessing to Laurent that he knew all along, once they've somehow sorted things out between them.

(Eventually Laurent's dilemma is resolved, when his superiors, despairing of ever getting this information, let Aymar go from Arbelles and Laurent decides to pull a Keith Windham and abandon his duty to go and care for Aymar instead.)