Is this the end of the great bond bull market?

What's going on in the world's government bond markets? All of a sudden, yields are rising fast again. In other words, sovereign bond prices are plunging. And we're not just talking about the likes of Ireland, where the yield surge has been driven by the recent bailout. (Yesterday, by the way, Fitch Ratings slashed the Irish credit rating for the second time in two months). No, we're talking about the planet's big boys – or should I say big borrowers. You can now get between 0.5% and 0.75% a year more by buying a ten-year US, UK or German government bond than you could two months ago. Even yields on Japanese sovereign debt, traditionally the lowest of the lot, have climbed sharply. So are we now finally seeing the end of the great long-term government bond bull market? If so, why – and what's next?