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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Flood warnings and alerts are in place for Scotland and northern England, while high temperatures are set to continue further south.
The state recorded 331 new cases on Tuesday.
Researchers used the method to study why flocks of long-tailed tits segregate themselves into different parts of the landscape.