3Where in England or Wales a person who has attained the age of seventeen is charged before a magistrates' court with an offence specified in Schedule 1 to the [1952 c. 55.] Magistrates' Courts Act 1952 and is also charged before that court with an offence under section 17(1) or (2) of this Act, then, notwithstanding anything in section 19 of the said Act of 1952, the court shall not proceed to the summary trial of the first-mentioned offence if the accused is committed for trial in respect of the offence under section 17(1) or (2) of this Act.