Those pointing out this has nothing to do with aviation security are largely correct; he would have been arrested if he had been stopped and searched by plod on Oxford Street; it just so happens it was a crew search at LHR instead. It wouldn't have made any difference if it was a pax search. It wouldn't have made any difference if they were found in checked bags. The possible offence is simple possession.
I think he may have a very strong defence. If you carry knives on Oxford Street, as others have pointed out, you need a 'reasonable excuse'; you need them for your work, you're off on a fishing trip, or something. If you carry them at LHR, about to board a flight, the excuse is bloody obvious - you're taking them out of the country! I'm sure Flying Lawyer would be able to advise us.
My stupidest security story? A few years ago I was pax out of JFK. TSA confiscated a tiny - 3" long, weighed a couple of ounces - adjustable spanner. When asked why, they looked puzzled, were obviously trying to think up an explanation, then one of them blurted out: "you could MAKE something with it!"...