Yup. You can own a Samurai sword if you want. Or a cannon perhaps. He can't carry it in public places unless he can provide good reason for doing so, eg for work or he's out in the woods etc, but it's perfectly legal to import and own. We still allow tools in the UK, despite fat men in suits with no practical bone in their body trying to make themselves look useful.
I would declare it as 'cutting tool' or 'camping tool' for the purposes of customs though.
Here's an over view of UK knife laws
http://www.goxplore.net/guides/Knife_law_(UK)
I really think a lot of the fuss has more to do with media hype and politicians trying to score points than it does with real life violent crime. There's a guy campaigning for mandatory jail sentencing for knife carriers. The daily mail's portrail of life in Britain is so bizarre, i think people like to feel outraged and imagine that britain is a dangerous place. By contrast my neighbour walks around with a shotgun over his arm and noone says a thing. A large contrast between the media (and government) portrail of violent crime and the real world over here.