I'm keen to hear if anyone has encountered this situation:
Benny’s LH and cavalry had advanced on opposite sides of the hamlet, so they were not lined up. The Numidians were positioned to ZoC both of them. Benny attacked with the Cv and the Numidians conformed (as he couldn’t). He then could close the door with the LH. Fortunately I won the battle. It’s an odd situation. Benny’s cavalry couldn’t advance as a group, as they weren’t one. He didn’t set out to create such a situation, but it was a nasty one.
Would have been tempted to fight as if overlapped or just moved front LH into combat...couldn’t then close the door
It was Benny's move, so he moved the Cv into contact first; conforming happens straightaway (it's not entirely clear, as the rules don't specify two individual elements and conforming, but as Benny couldn't and I could, I conformed), and then the LH was able to overlap or even close the door.