If a couple collude in getting a divorce on the grounds of adultery, did the husband actually have to commit adultery?

Not necessarily. The hotel divorce was a set-up -- an event staged to gather evidence. Sometimes the other woman was hired to play the part. Basically, the couple lied and presented evidence that would tend to suggest adultery by one or the other. Carried out in secrecy, adultery easily lends itself to meeting the two-prong test: the disposition and opportunity rule created a presumption of adultery if it could be shown that the two people in question had an "adulterous disposition" and had the opportunity to commit adultery. It was not be hard for a couple to collude on the disposition and opportunity rule.

An adulterous disposition usually means showing romantic involvement or entanglement of some sort. Love letters or public (or even semi-public, as we have seen) displays of affection are considered evidence of an adulterous disposition. The opportunity to commit adultery means showing that the two people in question were alone for a time. Basically, the opportunity to commit adultery means the parties in question had the time and the place.