Second movement opportunity charge discipline test

During tonight game a Unit of Imperial Reiters wheeled and moved foward during the movement a Swedish unit took the opportunity to charge The Swedish player announced the charge after the Imperials had failed the discipline test at eh end of their movement. Thus charged a disordered unit. As the player with the most knowledge of the game I said this wasn't allowed as the movement was completed so was not been interrupted and the Swedes were taking advantage of the disorder. Should the Swedes declared the opportunity before the discipline test to complete the second move? Also if the opportunity was only half way through the second move thus stopped the move when should the discipline test be taken? I assume once the charge has stopped the unit moving but best ask to confirm.

I'd be inclined to agree, a reaction can interrupt an enemy unit's move at any point but the DT occurs after the move so you can't interrupt after it is taken.

I would take the DT once the unit's move is complete - ie finish the interruption, then the unit finishes its move as best its able. Then it takes the DT after completion.

you should not declare a reaction after the result of the test. You can declare the reaction after the second move, and in case you should stop your opponent to roll the test and declare your intention before he rolls.

Thank you for clarifications chaps