It's always unwise to rely on newspaper reports, and we don't know the full facts of this case. However the government's own website advises that a folding knife with a blade of less than three inches is legal, but if it is used in a threatening manner it becomes an offensive weapon.

The man in this case pleaded guilty to carrying an offensive weapon, he doesn't appear to have been charged under the Criminal Justice Act (which specifically excludes small folding knives). It's not clear whether he was unaware of the law, just wanted to get the whole thing over, or whether there are other circumstances which were not reported.

If you carry any other type of knife, that's unlawful unless you can show a good reason for carrying it at that particular time (apart from some knives which are banned outright). Carrying a knife on the off-chance that you might need it seems not to count as a good reason. Ragdall might be in the clear if he's actually carrying fruit and intends to eat it at the time he's stopped, but possibly not if he keeps the knife in the car on other occasions.

I'm now wondering whether the Swiss Card I carry in my wallet is legal. It includes a small knife - the blade is only 1.5" but it's fixed - and a pair of tiny scissors. I suspect it's not and I would have to prove a "good reason" for carrying it.

Knife crime is a real problem and too many young men have died. However these rules are ridiculously strict (or are being enforced incorrectly by the police) and criminalise ordinary people going about their daily business for carrying a useful tool with them. The onus is on the accused to prove "good reason" and the courts may not agree.