]I agree that he uses disguise but what I meant was that he might have problem convincing Mr Bingley of something he did not believe to be true. In the case of Jane being in London he could just keep silent.

I belive that Darcy at first belived that there were no fellings on Janes side, probably because he wanted it to be that way. Then it wouldn't have been such a problem to convince Bingley. But I think that he must have known that Jane had some fellings from Bingley when she was in London. Perhaps if he had had the conversation with Bingley then he would have had a harder time trying to convince both Bingley and himself. As it is I belive that Darcy wouldn't admid to be wrong, since he so finaly have said that there sre no felling of Janes side.