After charges have been declared, if any Impetuous units did not declare a charge but are within charge range of an enemy, then they must take a Leadership test to restrain themselves from charging. If this test is failed, they are forced to charge. If the test is passed, they may move normally.
In addition, so reckless are the Knights Errant, that whenever they charge, the unit and any characters that have joined them are Immune to Psychology for the rest of that turn.

Purebreed Warhorse

For generations, the Bretonnian Warhorse has been bred to bear the weight of a fully armoured knight. Bretonnian Warhorses do not suffer any movement penalties for being barded.

Knights Vow

Knights with the Knight's Vow may ignore panic caused by friendly units and models with the Peasant's Duty.

Glory or Death!

Knights Errant suffer the following modifiers to any Impetuous test they take (this is cumulative with the -2 modifier due to the Errantry Banner itself).

-1 if there is one or more fear-causing enemies within charge range.

-1 if there is one or more terror-causing enemies within charge range.

-1 if there is one or more dragons within charge range (including undead Zombie Dragons).

-1 if there is one or more Damsels within 6" (they like to show off in front of the ladies).

-1 if there is one or more enemy unit within charge range that has a higher Unit Strength than the Knights Errant unit.

In addition, Knights Errant must always pursue. They roll an extra D6 in pursuit, and choose the highest three dice.