Could this be the trigger for a sterling crisis?

'Bubble' is one of those terms that gets bandied about rather liberally, with no one quite agreeing on what it means. Some say it's merely a rapid price rise, with a contraction to follow. Others say it's a rapid price increase, which bears no relation to underlying economic fundamentals. This creates an artificial market, meaning that rapid drops are inevitable. I like to define a bubble as “a bull market in which you don't have a position”. All three of these definitions could easily be applied to the US long bond (the 30-year Treasury) and UK gilts. So are these governments bonds in a bubble? And if so, when will it pop? And what will the consequences be?