"(1) Where a person under [the age of l8 years] appears or is brought before a magistrates’ court on an information charging him with an indictable offence other than ... he shall be tried summarily unless— ... (b)he is charged jointly with a person who has attained [the age of 18 years] and the court considers it necessary in the interests of justice to commit them both for trial."
"... it is now wholly clear that whenever a court is confronted by failure to take a required step, properly or at all, before a power is exercised ('a procedural failure'), the court should first ask itself whether the intention of the legislature was that any act done following that procedural failure should be invalid. ... 5. On the other hand, if a court acts without jurisdiction – if, for instance, a magistrates' court purports to try a defendant on a charge of homicide – then the proceedings will usually be invalid."