What evidence will be considered on an application to vary?

With respect to the evidence to be considered on an application to vary, guidance was provided by Hart, J. (as he then was) in Wesson v. Wesson, (1973), 10 R.F.L., p. 193, at p. 194: In my opinion the evidence to be adduced in support of such an application should be limited to the changed circumstances of the parties subsequent to the latest order of the court. This is not to say that cross-examination should be limited to recent events if reference to earlier facts is necessary to determine the credibility of any of the witnesses, but it must be assumed that the order of the court was validly made in accordance with the law if it has not been previously set aside Once the evidence of the changed circumstances has been received, however, the court must be guided in making its decision by the well-established principles of law relating to custody applications.

In Wesson v. Wesson, supra, there were changes in the circumstances of both parties. Justice Hart described then as considerable. Nevertheless, he maintained the status quo.