Whilst playing a doubles match at my club (social but of a high standard), during a rally, a player from the next court let his momentum carry on into our court on my opponents side. This intrusion occurred whilst the shuttle was at my opponents end. I called Let as soon as I noticed but I was a bit slow so it was called after my opponent had hit the shuttle and when the shuttle was on it's way back. The rally stopped and my opponent said it was not my place to call Let because the invasion happened on his side during his shot. My immediate thought was of embarrassment for calling out Let when I thought I shouldn't have so I offered him the point for the rally and we carried on. After we finished the game, I started to think about this and then thought that had the intrusion been a shuttle from the next court then it wouldn't have mattered who called Let or who was affected by the shuttle. If a shuttle intrusion happened and someone called Let as soon as they noticed then it was valid. It seemed bizarre if this thinking didn't apply to a player invasion as well. Was my opponent right in his statement or was my call for Let valid?