It doesn't take much for Britain's sewerage system to be overwhelmed.
Heavy rain had been forecast for the southeast of England on Saturday morning, with an amber weather warning issued.
In fact, the downpours weren't as intense as feared - and they were brief.
Yet, sewage overflows across the region quickly began discharging into rivers.
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Data from The Rivers Trust shows that at midday on Saturday there were 75 outlets actively pouring effluent into rivers in the southeast.
And another 164 had been discharging in the previous 48 hours.
It's been worse - far worse - in the past.
But the sewage was being discharged into rivers heavily impacted by weeks of hot, dry weather.
Not only was the water temperature higher than normal, reducing oxygen levels and encouraging blooms of algae, but river levels were low, so there was less water to dilute the sewage.
It's a double whammy for aquatic life.
It reflects years of underinvestment in the infrastructure. The crumbling sewerage system hasn't kept pace with the growth in the population.
The priority of the water regulator Ofwat has been to keep customer bills low, at the expense of the environment.
And we are now paying the price.
The Water Commission's report next week is expected to recommend much tighter regulation in future, and Ofwat is likely to be abolished.
But it will take billions of pounds and many years to clean up our rivers.
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