Fears that Britain may be heading for its first sovereign debt crisis since the 1970s hit a new intensity after Pimco, the world's biggest bond house, declared that it is starting to sell off its holdings of gilts.The American investment group said it will be a net seller of UK Government bonds this year, at the very point when the Bank of England brings its £200bn programme of purchases to and end and the Treasury attempts to raise unprecedented sums through the capital markets. The move is doubly embarrassing for the Government because the head of Pimco's European investment team...