I've just viewed a video on Boardgamegeek which has made me think that I have misunderstood the overrun rule. The example showed 3 Roman armies moving into a space with one defending army. The example then left 1 army in the space and advanced with the other 2.
The rules say that you must have more than double the number of defending armies and then the excess may keep moving. I've always thought that the excess referred to the amount which was greater than more than double. So if 1 army is defending then 3 have to remain in the space and any others can keep moving.
which is right please?