Rating agency Moody’s has downgraded the UK’s credit rating outlook to "negative" after the country voted to leave the EU. Moody's said the result would herald "a prolonged period of uncertainty". Moody's said the referendum result would have "negative implications for the country's medium-term growth outlook". It also lowered the UK's long term issuer and debt ratings from "stable" to "negative". The pound plunged and world stock markets slumped Friday after Britain's shock vote to leave the European Union, fuelling a wave of global uncertainty. Sterling crashed 10% to a 31-year low at one point and the euro also plummeted against the dollar, as the Brexit result caught markets by surprise.