They admitted some facts. They relied on a police officer not to caution them when the offence hadn't been committed. It possibly hadn't been committed. Only clear cut cases are suitable for cautions, and this isn't clear cut.
As to the rest, there are rules about how the police must behave. It isn't about treating kids with kid gloves, it's about not treating police officers with kid gloves. They have to abide by the rules.
As to the rest, there are rules about how the police must behave. It isn't about treating kids with kid gloves, it's about not treating police officers with kid gloves. They have to abide by the rules.