LONDON - In theory, prospects for a peaceful settlement on the Korea peninsula have seldom been better; Friday's (Apr 27) summit between North Korean leader Kim Jong Un and his South Korean counterpart Moon Jae In is set to be followed by a US-North Korea summit, a truly historic encounter which could usher a spectacular process of nuclear disarmament.

But although optimism is a good starting point for summits, hopeful sentiments are never a good ingredient to their ultimate success. For the diplomatic road ahead will be long and hard, and attention to the technical details of any deal will be much more important than the immediate photo opportunities generated by such gatherings. Nor is it very clear that the various participants share the same understanding about the building blocks of a future settlement. And nowhere could differences in perception be greater than in the very concept of nuclear disarmament.