Written statement Amendment

What are the facts? What is the context?

Or. 6 R. 17 :  Amendment of Pleadings : The Court may at any stage of the proceedings allow either party to alter or amend his pleadings in such manner and on such terms as may be just, and all such amendments shall be made as may be necessary for the purpose of determining the real questions in controversy between the parties:   Provided that no application for amendment shall be allowed after the trial has commenced, unless the Court comes to the conclusion that in spite of due diligence, the party could not have raised the matter before the commencement of trial. 

 while allowing amendment of a written statement, general principle is that the amendment should be allowed even if it amounts to addition of new grounds of defence,substituting or altering a defence or taking inconsistent pleas in the written statement