The defendant has to apply for leave to appeal against the sentence.This is not for the Crown Court judge.. The defendant applies to the Court of Appeal.. This is done by his lawyer submitting a written opinion why the sentence is wrong together with some short, draft grounds of appeal.These are read by 'the single judge', a High Court judge assigned to considering these applications, who rules on them. The single judge is not going to grant leave to appeal if the sentence is within the guidelines for sentencing for such offences unless persuaded that the Crown Court judge missed, or didn't apply enough weight to, some factor which should have been taken into account in that individual's case.It might be that the sentence would be correct in most cases but unjust in this particular one.