Boris Johnson has visited residents evacuated from Whaley Bridge, a Derbyshire town near the Toddbrook Reservoir, which is at risk of being wiped out if the dam collapses.

An RAF helicopter has been drafted in to repair the dam amid fears it could collapse in what police have called an “unprecedented, fast-moving, emergency situation”.

The reservoir contains around 1.3m tonnes of water.

“The plan is to try and stop the dam breaking, clearly. And so a huge amount of effort is going into that,” Mr Johnson said to a group of residents when he visited the town on Friday evening.

“The Chinook’s been over putting in the aggregate and putting in the sandbags to try and stop it bursting. They’re pumping out huge amounts of water.”

Whaley Bridge dam emergency in pictures Show all 13 1 /13 Whaley Bridge dam emergency in pictures Whaley Bridge dam emergency in pictures The damage of a dam in Whaley Bridge is seen after a nearby reservoir was affected by flooding REUTERS Whaley Bridge dam emergency in pictures A damaged dam is seen after a nearby reservoir was affected by flooding, in Whaley Bridge, Britain August 1, 2019. REUTERS/Phil Noble PHIL NOBLE REUTERS Whaley Bridge dam emergency in pictures The damage of a dam is seen after a nearby reservoir was affected by flooding, in Whaley Bridge, Britain August 1, 2019. REUTERS/Phil Noble PHIL NOBLE REUTERS Whaley Bridge dam emergency in pictures Emergency services at Toddbrook Reservoir near the village of Whaley Bridge, Cheshire, after it was damaged in heavy rainfall. PRESS ASSOCIATION Photo. Picture date: Thursday August 1, 2019. See PA story WEATHER Rain. Photo credit should read: Danny Lawson/PA Wire Danny Lawson PA Whaley Bridge dam emergency in pictures Damage caused to the Dam Wall at Toddbrook Reservoir in Whaley Bridge following heavy rainfall in the area @fraglast/PA Wire Whaley Bridge dam emergency in pictures Picture taken with permission from the Twitter feed of @fraglast of damage caused to the Dam Wall at Toddbrook Reservoir in Whaley Bridge, Derbyshire following heavy rainfall in the area. PRESS ASSOCIATION Photo. Picture date: Thursday August 1, 2019. See PA story WEATHER Rain. Photo credit should read: @fraglast/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. @fraglast @fraglast/PA Wire Whaley Bridge dam emergency in pictures A team of men look at the damage to the wall of Toddbrook Reservoir near the village of Whaley Bridge after it was damaged in heavy rainfall PA Whaley Bridge dam emergency in pictures Picture taken with permission from the Twitter feed of @fraglast of damage caused to the Dam Wall at Toddbrook Reservoir in Whaley Bridge, Derbyshire following heavy rainfall in the area. PRESS ASSOCIATION Photo. Picture date: Thursday August 1, 2019. See PA story WEATHER Rain. Photo credit should read: @fraglast/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. / re: A reservoir in Derbyshire has been cordoned off by emergency services following fears it could collapse. Police are telling people to stay away from Toddbrook Reservoir in High Peak, which appears to have suffered substantial damage. Photos show the dam wall with what looks to be a huge hole at the side. A number of roads are in place, and Whaley Bridge Memorial Park is also closed. @fraglast @fraglast/PA Wire Whaley Bridge dam emergency in pictures Picture taken with permission from the Twitter feed of @fraglast of damage caused to the Dam Wall at Toddbrook Reservoir in Whaley Bridge, Derbyshire following heavy rainfall in the area. PRESS ASSOCIATION Photo. Picture date: Thursday August 1, 2019. See PA story WEATHER Rain. Photo credit should read: @fraglast/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. / re: A reservoir in Derbyshire has been cordoned off by emergency services following fears it could collapse. Police are telling people to stay away from Toddbrook Reservoir in High Peak, which appears to have suffered substantial damage. Photos show the dam wall with what looks to be a huge hole at the side. A number of roads are in place, and Whaley Bridge Memorial Park is also closed. @fraglast @fraglast/PA Wire Whaley Bridge dam emergency in pictures Emergency services at Toddbrook Reservoir near the village of Whaley Bridge, Cheshire, after it was damaged in heavy rainfall PA Whaley Bridge dam emergency in pictures Picture taken with permission from the Twitter feed of @fraglast of damage caused to the Dam Wall at Toddbrook Reservoir in Whaley Bridge, Derbyshire following heavy rainfall in the area. PRESS ASSOCIATION Photo. Picture date: Thursday August 1, 2019. See PA story WEATHER Rain. Photo credit should read: @fraglast/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. @fraglast @fraglast/PA Wire Whaley Bridge dam emergency in pictures Emergency services in the village of Whaley Bridge, Cheshire PA Whaley Bridge dam emergency in pictures A roadblock is put in place at Whaley Lane PA

“We’ve had an exceptional weather event, we must make sure that this dam can cope with it in the future,” he added.

“That will mean a major rebuild, clearly.”

The reservoir’s spillway partially crumbled on Thursday after heavy rain fell in the area.

The RAF Chibook has dropped around 400 tonnes of sanbags in an effort to repair the dam.

But officials said it was unclear how long the crisis would go on for. The reservoir’s water level has dropped by half a metre, but needs to drop by several more metres to be considered safe.

“We will be putting plans in place for residents to return to their home to pick up very vital things they need along with their animal welfare,” said Kem Mehmet of Derbyshire Police.

“This is very controlled, I must stress that, because this is still life at risk.”

Police have closed railway lines in the Whaley Bridge area over the risk of potential flooding.

The reservoir is on the north-west edge of the Peak District National Park and was built in 1831, according to experts, although the Environment Agency records it as being built in 1840-41.

Meanwhile, clean-up operations are under way across parts of the North West hit by heavy rain. Residents in Poynton in Cheshire were also evacuated on Wednesday night.

If you would like to see how the emergency response unfolded live, please see what was our live coverage below: