Question posed by a Player (Wizard Camelot)

There are four cards played in a trick, in this order: Excalibur, Merlin, Jester, Jester.
If a person LEADS Excalibur in a trick, nullifying the trick, who leads the next card?
Answer:
Trick Number 5 (perhaps).
Player A leads Excalibur which nullifies the trick.
Player B plays Merlin as a Jester.
Player C plays a Jester.
Player D plays a Jester.
Who wins the trick?
Answer. Player B as he played the first Jester.
Ergo player B leads for trick number 6.

OR

Trick Number 5 (perhaps).
Player A leads Excalibur which nullifies the trick.
Player B plays Merlin as Wizard.
Player C plays a Jester.
Player D plays a Jester.
Who wins the trick?
Answer.
Player B as he played the Wizard.
Ergo player B leads for trick number 6.

Another example

Trick Number 5 (perhaps)
Player A leads EXCALIBUR which nullifies the trick.
Player B Plays Morgan le Fay (perhaps he does this because he has already made is bid and needs to get rid of the winning card. He knows that although he wins the trick that it will not count as the trick has been nullified.
Player C plays the 2 clubs.
Player D plays the 10 of Spades.

Trick Number 6
Player B won the previous trick (although it does not count on the scorepad)
Ergo, player B leads trick number 7