Ofwat's decision to reject Thames Waters' bid to increase prices by 8% is final, but Thames Water could appeal to the Competition Commission.
The company said: "We will review the decision carefully before deciding on our next steps."
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The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
A police spokesman said the incident in the Bourke Street Mall on Friday was not related to terrorism.