“It is in general a salutary principle that those who lose discrete aspects of complex litigation should pay for the discrete applications or hearings which they lose, and should do so when they lose them rather than leaving the costs to be swept up at trial.”
“In exercising that discretion, the overriding objective is of the greatest importance. Applications always involve the court striking a balance between injustice to the applicant if the amendment is refused, and injustice to the opposing party and other litigants in general, if the amendment is permitted.”