Breach of Statutory Duty ka Twist

Question: A and B are neighbours, and a wall which is common to their houses is in a dilapidated condition. A has served a notice to B under the relevant building bye-laws to repair the wall. B does not comply and the wall collapses, injuring C, who is passing by. C sues both A and B for his injuries. A argues that he had fulfilled his duty by serving the notice and now B is liable only. Is A correct in his defence?

Most students will say A is correct, but there's a twist here. B's failure to repair the wall can also be seen as a breach of his non-delegable duty of care towards C, who has no relation with A or B. Most people get this question wrong because they don't know about the 'non-delegable duty' and think A's service of notice is enough.