Watch Max Walsh's report on the pollution incident here
Thousands of fish have been killed following a major pollution incident near Swindon after a sewer main burst.
Toxic sewage has been flowing into the River Ray since last Friday in what has been described by the environment agency as "the most serious" of pollution incidents.
The entire 7km stretch of water which connects to the River Thames has been affected and there are concerns about the ongoing impact on the surrounding countryside and wildlife that relies on the river as a water source.
Ash Smith has been campaigning against sewage pollution for years, but even he says he's shocked by what he's witnessed.
"It's appalling and it's unnecessary. This is about taking chances with our environment, letting infrastructure just break instead of proactively making sure it's safe.
"This is the consequence, completely killing a river - beautiful fish like this that took years to grow.
"There are tens of thousands of dead fish in this river and it didn't have to happen."
While the leak was detected on Friday, Ash believes it may have been going on for much longer, following the emergence of sewage fungus in the river which usually takes a week to form.
Thames Water is currently trying to recover the river by pumping oxygen back into the water.
They are using tankers to re-route the sewage whilst they complete the repairs and it's hoped that the restoration works will be finished by the end of the day on Wednesday.
The Environment Agency has been surveying the waterways and says that in one 200-metre stretch, they have found more than 1,000 dead fish.
“Environment Agency officers continue their emergency response to a serious pollution incident near Swindon this weekend that has resulted in the deaths of thousands of fish on the Haydon Wick Brook and River Ray.
“Our surveys show that the pollution has spread over 7km of watercourses, reaching the nearby River Thames. We have used aerating equipment to help reoxygenate the water to limit further damage to the local environment. Our investigations are continuing into the cause of this incident."
Residents living nearby say they are frustrated with the disruption, after having experienced a similar leak in the area just 15 months ago.
"It's been quite horrendous really, the noise, the smell and the total disruption to the track entering the estate 24/7 since this happened. It's just been unacceptable, unbearable really.
"The Thames Water engineers keep reassuring us that it'll not happen again.
"It's about high time Thames Water stop this sticky plaster approach to mending what is a much bigger problem."
In a statement, Thames Water spokesperson said: "When the burst occurred wastewater escaped into the River Ray.
"We, along with the Environment Agency, are monitoring the river’s water quality closely and have put in place steps to help the river recover, including aerating the river."
“We have also deployed a significant number of tankers in the area. They are connecting to our sewer network and removing wastewater.
"This allows us to access the broken pipe safely and protects local homes from flooding. We apologise if the tankers are causing any disruption to local residents, and we have customer teams in the area speaking to customers about our work to repair the pipe.
"When the repair is completed, the tankers will no longer be required but we will remain on site to reinstate the area. Our work will not affect our drinking water and wastewater services, customers will be able to use water and flush toilets as normal.”
Investigations are still ongoing to find out what caused the leak but for now, the community has been left dealing with the clean-up operation.