Couple of tips.
If he's a chef and he's carrying chef's knives (obviously hidding in a bag or something, not in his pocket or dangling from a belt) he will be ok as he has "good reason" to carry them. If he's taking them half-way round the world, the knies are clearly precious to him and he'll have them properly wrapped and safe so again that will help him if he's stopped.
If he uses a flick-knife for filleting chicken (god knows why he would) he'll get prosecuted as flick-knives are banned.
If they are prescious, he'll still need to put them in the aircraft hold of course and packing them well inside his case before he gets to the airport would be sensible. Airport security are probably less accommodating than a British Bobby.