This excerpt is from page 12 of the Warhammer Annual 2002 in the section titled, "AFTER 'EM LADS!"
In the case of units breaking from combat, enemy units are allowed to pursue, which can also throw up some odd situations. This is because a unit is wiped out if an enemy unit rolls equal to or higher than the flee move on its pursuit roll. This system is abstracted from the relative positions of the miniatures. When one unit is fleeing from a single enemy, this usually causes no problems. However, if attacked from two different directions, one of the pursuing units could have models in contact with the fleeing troops without having rolled equal to or higher than their flee roll. Diagram 6 (below) shows this.
To resolve this, I always look at the difference between the two rolls rather than the distances. Move the fleeing unit the distance rolled and then position the pursuing unit a number of inches behind equal to the difference, facing in the direction of the pursuit. When particularly low numbers are rolled, this may mean that the pursuing unit is actually slightly further back than when it started, but for me that's the lesser of two evils. When two or more units are pursuing, I place them their relative distances behind and evenly split along the line of pursuit (see diagram 7, below).