...if we had more information on exactly what passed. We never actually know that Denny had any foreknowledge of Wickham's plans, nor is it in character or in Wickham's interest (yes, interest ;-) to share such plans.

Denny's conviction that Wickham never intended to marry may have been an offhand response to gossip in the officers' mess where, after comparing how much Wickham owed them all, one officer postulated that Wickham had run off with Miss Bennet for Gretna Green. Denny's response could have been something as generic as, "Take Lydia to Gretna Green? Impossible! I am convinced Wickham will never marry anyone with less than 10,000 pounds."