Fitch has downgraded UK sovereign debt, following Moody's lead. Frances Coppola explains why they're wrong - I outlined similar thoughts over a year ago, but she is much more thorough.
Coppola starts by explaining that "For sovereign debt, [a credit rating] is supposed to give investors an indication of the risk of loss due to default". Yes, but it's hard to imagine a single investor's mind being changed on Fitch's say-so. The real purpose of these ratings is to get featured in the news.
The principal damage inflicted by the downgrade is on George Osborne and his colleagues, who undertook to "safeguard Britain's credit rating". And the only people helped by it are the ratings agencies, who have attracted a lot of respectful publicity. To sum up, a politician has failed to keep his promise, and a publicity seeker has successfully sought publicity.