Despite the deadlock in Washington, Standard & Poor's reassured markets that it had no plans for a further downgrade of the US credit rating. That shored up the FTSE 100 Index, which was up 41 points at 5263.6.
However, the focus in the City was on Thomas Cook shares, which have now fallen by 93% since the start of the year. They dived by 66% - 27.2p to 13.9p - to give it a market value of just £120 million.
Thomas Cook's stand-in boss insisted the company was "robust" but investors were spooked by its need for an additional £100 million in funding headroom over December and January - just a month after a similar request to banks. Rival operator TUI Travel was impacted by the update, with its shares down by 7% or 10.2p to 140.4p.
