Dougall v Crown Prosecution Service  EWHC 1367 (Admin)
Those plain words stipulate that a magistrates' court may not try an information alleging a summary offence unless the information on which the prosecution is founded was laid within the statutory time limit. That is so, whether the information initially charges the summary offence or initially charges an indictable offence but is later amended to charge a summary offence. If no information is laid within the period of six months, but an indictable offence is later charged and then subsequently amended to charge a summary offence, that amendment does not avoid the consequence of the statutory time limit.
1) An information charging an indictable offence was laid more than 6 months from the commission of the offence;
2) The prosecution then seek to amend the charge to allege a summary only matter;
3) In those circumstances, a summary only offence could not have been originally charged (as time barred) and therefore an amendment laying a summary only offence cannot be made.