What is the test for admitting further evidence after the close of a trial?

After reviewing several authorities, the trial judge stated: An examination of the foregoing authorities clearly establishes that a trial judge has discretion to admit further evidence after the close of the trial either for his own satisfaction or where the interest of justice requires it. This discretion has been exercised by different trial judges in many different situations and for different reasons, and I am inclined to agree with the remarks of Romer J., in the case of Barker v. Furlong, [1891] 2 Ch. 172 at p. 184, that where counsel had not been misled by anything falling from the other side that ‘in granting the plaintiff’s application after the defendant’s case had been argued and closed and reply begun, I should be making a precedent, which would, if established, lead to an improper amount of laxity in conduct of plaintiff’s case.’ However, in the case at bar the plaintiff has, in my opinion, been misled by the defendant’s defence in that the evidence led by the defence sets up a defence different from that set out in the pleadings.