2A provision contained in any of sections 18(2), 19, 21, 22, 27, 30 and 39 of this Act, and any such related amendment or repeal, shall not apply in relation to a trial which has commenced before the coming into force of that provision ; and, for the purposes of this paragraph, a trial shall be taken to commence—
(a)in the case of solemn proceedings, when the oath is administered to the jury ;
(b)in the case of summary proceedings, when the first witness is sworn.