15.—(1) Where one of concurrent wrongdoers who are sued together makes default of appearance or defence, the plaintiff may obtain an interlocutory judgment against him and damages shall be assessed against him—

(a) at the same time as damages are assessed at the trial against the other defendants who appear;

(b) if the plaintiff fails against such other defendants or discontinues his action against them, separately under the interlocutory judgment.

(2) If the plaintiff fails against the defendants who appear for a reason that goes to the liability of all, the interlocutory judgment shall be discharged.

(3) If the plaintiff’s damages against the defendants who appear are reduced under subsection (1) of section 34 on account of the plaintiff’s contributory negligence, damages shall be assessed under the interlocutory judgment as if the defendant had appeared.

(4) This section shall not apply to any head of damage in respect of which the defendant who makes default and the defendants who appear are not concurrent wrongdoers.