Actions Required to Control a Mount With Unmatched Speed

[prestidigitator]

Let's assume that a rider doesn't have ANY Phases (Segment+Dex) in common with his mount, and neither is Delaying their Phases to match the other's. Let's also assume that the rider and mount have different Speed Characteristics.

I assume the rider must still take a Half-Phase during some of his Phases in order for the mount to do as he wishes in its own Phases (if he wishes a trained mount to act or an untrained mount to keep from panicking). The question is, in how many of the rider's Phases must he take this Half-Phase to control the mount. Is it:

A.) All of them, no matter the Speeds of the rider and mount.
B.) A number of Phases equal to the mount's Speed. Don't worry about the relative order of their Phases. If this is the answer what happens when the mount has a higher Speed? Must the rider take two Half-Phase Actions in some of his Phases to match the mount's Speed, or do we just assume that as long as he does a control action every one of his Phases--even if fewer than the mount's--we are good?
C.) A number of Phases equal to the mount's Speed, never allowing the mount to get two Phases without a control action inbetween (in this case I assume the rider may have to delay some Half-Phases to act between two of the mount's Phases; whew!).
D.) Other (please give a little clarification if you would).

Thanks!

[Steve Long]

The rider needs to devote a Half Phase Action to this in each of his Phases, up to a maximum number of the mount’s Phases or his Phases, whichever is less. He cannot “combine” two Half Phase Actions into one Full Phase Action to “free up” a Phase in which he doesn’t have to do this.