What are the principles to apply in the context of a motion by a plaintiff to have his case considered on the merits of the motion?

The principles to be applied in these cases were set out by Twaddle J. A In Law Society of Manitoba v. Eadie (1988),[1]: It seems to me the fundamental principle is this: A litigant is entitled to have his case decided on its merits unless he is responsible for undue delay which has prejudiced the other party. . . . I prefer to put all relevant considerations into a balance and decide, as a single question, whether it is just to take away from the litigant responsible for the delay the right to have his case determined on its merits. This involves, of course, the difficult task of balancing the basic right of that litigant with the right of the other party not to have his rights prejudiced by undue delay. Amongst the matters which should be taken into account on a motion such as this are: (i) the subject matter of the litigation; (ii) the complexity of the issues between the parties; (iii) the length of the delay; (iv) the explanation of the delay; (v) the prejudice to the other litigant.