Slitherine

During one of the games at Devizes, the following situation arose. A 3-base unit of my horse (D) had advanced to just a few mm short of a 4-base enemy cavalry unit (E); you could literally only just see the table between their bases, aligned thus with E having a one-base overlap on my right flank:-

E-E-E-E
D-D-D

As a result of other activities during the subsequent enemy phase, another enemy cavalry unit (E2) arrived at right angles to the first, and just outside their left flank, facing the right flank of D, thus:-

E-E-E-E
D-D-D...E2
..........E2

The distance between E2 and D was slightly more than a full base width, but just under two inches. Next turn, D declared a charge against E, at which point my opponent announced that I could not charge as E2 had carried out an intercept charge and stopped me reaching E. The distance between D and E was literally just a couple of mm, the distance between D and E2, was approximately 25 times that distance; and D would still have remained substantially within the outer line/zone of control of E2 had its charge gone home.

Surely the distance for an intercept charge needs to be less than the actual charge in order to stop it, otherwise the original charge gets there first?

This was played correctly according to the rules, if an intercept charge is a legitimate flank charge the original charge is cancelled (P86).

As to the logic, you'd need to question the authors, but I'd guess that the answer might be that the consternation caused by being charged in the flank would cause the intercepted BG to abandon its intended charge.