Simon Cowell says his £15m mansion 'nearly floated away' - as experts blame super-basements, ancient drains and THREE INCHES of rain in 90 minutes for 'biblical' flooding in Kensington and Chiswick

X Factor boss Simon Cowell's £15million mansion was hit by 'biblical' flash flooding that caused millions of pounds of damage to properties and was today blamed on sprawling super-basements.

The 61-year-old TV and music star was spotted near his West London home as families and businesses dealt with the waters which had cascaded into homes, ruining treasured possessions and mementos and causing expensive damage.

Wearing his trademark plain black T-shirt and white shorts Mr Cowell seemed in reasonably good spirits despite hinting his home may have suffered from the floods.

Asked whether he had escaped the flooding, he admitted 'not really, my house nearly floated away'.

Sprawling super-basements dug beneath London's homes have today blamed for the flooding.

The enormous underground caverns - popular with the wealthy wanting to expand their space - were criticised by experts and victims of the massive leaks as they counted the cost of the weather today.

Kensington and Chiswick were been particularly hard hit as three inches of rain made it the third wettest day for West London on record.

Last night flood waters also poured through the streets of Portobello Road in Notting Hill after nearly three inches of rain hit the capital in just 90 minutes and in Raynes Park, south London, cars were left abandoned in around 2ft of water after torrential downpours caused travel chaos and left homes and businesses flooded.

Meanwhile in Turnpike Lane, north London, people were spotted wading through the water in the streets as the heavy rain pelted down and flooded the roads.

Flooding expert and campaigner Mary Dhonau OBE told MailOnline flooding was caused by a jigsaw of different factors.

But the consultant, who has previously been chair of the National Flood Forum, said the rise of the 'super-basement' would have contributed.

Undeveloped grass and land can easily absorb heavy rain if and when it falls, soaking up the water like a sponge.

But if it has been removed it means there is nowhere for the liquid to go, causing flooding.

Ms Dhonau said: 'There has got to be somewhere for the water to go. When there is rain it falls onto the ground and percolates in areas of the ground. Super-basements are being built where the water would naturally percolate.

'There are other factors like climate change, but the more we take away permeable surfaces the more places will flood.

'North Kensington is a prime example of land that would have soaked up water, which is now being used for super basements.

'It is a jigsaw of things that can cause flooding. You can do things to make flooding more likely and one of those things is using more land for super-basements.'

Queen guitarist Brian May, who also lives in the area, said he was heartbroken and devastated after coming back to the 'horror' of finding his basement flooded with a sewage overflow which destroyed carpets, rugs and precious photos and memorabilia from over the years.

Brian, 73, who is married to former Eastenders actress Anita Dobson, 72, posted a video on his Instagram to show the extent of the 'disgusting' damage in their £7million home.

He admitted he didn't 'know where to start' as he showed off the 'stuff' including ancient photos from his childhood strewn and dirtied everywhere at the bottom floor of their house.

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He said: 'Just when you think everything is ok, nothing else is going to bite you, you can deal with life'

'It feels like we were have been invaded, desecrated. Anita had a lifetime of memorabilia on the floor of our basement - and most of it is sodden and ruined. I had rescued all my most treasured childhood photo albums and scrapbooks from my studio house because it was threatened with a forest fire some months ago.'

'Where did I put it all for safety ? In the basement here in Kensington. Irony. Today it turned into a sodden mess.'

'Historically, for 150 years, Kensington has never flooded due to rainwater. Why did this happen ? It's almost certainly the result of all the basement building that has been plaguing this area for the past 10 years.

'The Royal Borough of Kensington and Chelsea council was warned years ago that sinking so many deep basement extensions would obstruct the aquifers underneath our living space and render the drainage system ineffective.'

When is planning permission needed for new basements?

Creating a basement in your home will only require planning permission in certain cases.

This includes converting an existing residential cellar or basement into a living space when it is a separate unit, significantly altering the usage or a adding a light well to change how the property looks.

Permission is also needed when you excavate to create a new basement which involves major works.

Creating a basement from scratch will probably need permission and building regulations are different if the basement is to be used as a 'habitable' space.

This includes providing a fire escape route, proper ventilation and a defined ceiling height.

However, generally permission for a conversion is not needed unless you are changing the look of the outside of the house or the building is listed.

She told MailOnline: 'There were about 12 inches of water that hit my home. Fortunately I was out when it happened and I got the alert something was wrong.

'It is the basement of my house, which is where my office is located, so a lot of my files down there have been ruined. Fortunately I have a back up of most things on my computer.

'I am ringing the insurers this morning. My neighbours also had about the same amount of water come in. It was dark water, it's never happened before. I'm sure there is a lot of damage in the area, fortunately it seems to be mostly in basements.'

Jacqui Barber, 60, told MailOnline: 'I was in the house and there was a lot of rain and it was torrential coming over the top of the houses.

'I heard a gurgling sound and water started coming up in the toilet. I flushed it and it went down again but the next thing we knew it was pouring through the front door and was up to our knees.

'It went up to our knees in sewage water, nothing could be saved. We have lost tens of thousands of pounds and we are not insured.

'We have managed to get a lot of the stuff out and it's now all at the front of the property. It was my daughter's flat in the basement and I live above so she is coming up with me. She is nine months pregnant.

'People are out in the streets today just dragging their belongings out. One of my neighbours is insured but they are told me they've been told it isn't covered because it's classed as a national disaster.'

In other scenes, Sloane Square tube station in Chelsea was forced to shut down after fast flowing water poured down the steps of the underground and in South Hampstead motorists desperately tried to navigate their way through the roads as the heavy rainfall continued to fall.

Friend’s video of Portobello Road. Crazy. pic.twitter.com/JE5i6C0C6Q
— Sophia Money-Coutts (@sophiamcoutts) July 12, 2021

Friend’s video of Portobello Road. Crazy. pic.twitter.com/JE5i6C0C6Q

Cars are left abandoned in around 2ft of water after heavy rain falls on a road in South Hampstead, north London, yesterday

Flood waters poured through the streets of Portobello Road in Notting Hill after nearly three inches of rain hit the capital in just 90 minutes yesterday

Rain batters the streets of London forcing cars to drive through inches of rain during thunderstorms in London last night

It wasn't all mayhem, as mechanic Andy Simmons downed tools and brought out the jet-ski he stores at his garage in Poole, Dorset

Cars are abandoned in water after torrential downpours left roads flooded in Turnpike Lane, north London, yesterday

In St John's Wood, one homeowner was left shocked as water began to splurge out of their overflowing toilet through their property

Roads are flooded in Maida Vale, west London, after heavy rainfall hits the capital - with nearly three inches of rain hitting the region in just 90 minutes

People sprint through the streets of Highgate in north London with their umbrellas to get out of the torrential downpours

The rapid rise of the super-basement

The super-basement concept is one that has only come to prominence over the past 20 years.

It became popular because many of the areas favoured by the super-rich also carry restrictive planning regulations.

This means the only option is to go further down and fashion an expansion digging into the earth.

It often means the size of the underground extension can nearly be as big as the original property itself.

The so-called 'Iceberg homes' up to 59ft (18m) deep are being placed into Britain's richest areas such as Kensington and Chelsea.

They include astonishing amenities including artificial beaches and even car museums.

Turkish baths, cigar rooms and banqueting halls are also among the features, with around 1,000 gyms, 380 pools, 460 cinemas, 380 wine stores and 120 staff rooms found in basement plans in the capital between 2008 and 2017.

The combined depth of every basement approved by seven London boroughs in the past decade is 50,160ft (15,289m) - 50 times the height of The Shard – with two of the basements said to include multiple pools.

Researchers at Newcastle University found there were 785 large basements - going at least two storeys under the house, or one storey far under the garden, in the study carried out for The Guardian .

A further 112 were 'mega basements' – at three storeys in depth or two far under the garden. Some 67 are in Kensington and Chelsea, while another 34 are in Westminster.

The basements feature a total of about 550 media rooms, 340 games rooms, 240 saunas or steam rooms and 60 underground garages and parking facilities.

Elsewhere, in St John's Wood, one homeowner was left shocked as water began to splurge out of their overflowing toilet through their property.

MPS Westminster also reported heavy flooding around Colville Terrace, Holland Road and Ladbroke Grove and said the emergency services were now evacuating areas due to flooded properties and collapsed ceilings.

A spokesman said: 'Reports of heavy flooding around Westminster including Colville Terrace, Holland Road and Ladbroke Grove Emergency services assisting in evacuating areas due to reports of flooded properties and collapsed ceilings. Road closures are in place.

It came as the Met Office issued a yellow weather warning for rain for a large section of southern England and the Environment Agency issued one flood alert for areas close to the upper River Loddon in Basingstoke, Hampshire.

As the intense downpours ensued, the London Fire Brigade confirmed they had received more than 1,000 calls related to flooding and urged people to 'only call if there was a genuine emergency'.

A spokesperson for the service said: 'We're asking people not to walk through or drive through the flood water. Flood water can be contaminated and vehicles can become unstable.

'We're also asking people to look out for their neighbours and look out for weather warnings in their area.'

Yesterday, Euston Station lines had to be shut down and underground stations, including Chalk Farm and Hampstead stations in north London and Wimbledon in the south, also drew their barriers due to the heavy rainfall.

A Network Rail spokesperson said: 'The line between Watford Junction and Euston has been closed and engineers are on site inspecting the track as the water recedes. As soon as it is safe to do so, we will have trains on the move again.

'We would advise anyone travelling this evening to check with their train operator or the National Rail Enquiries website for the latest information.'

The flooding problems appear to be concentrated in south west and north west London, including boroughs such as Richmond and Kingston.

Last night, residents in a number of areas such as South Hampstead, West Hampstead, Raynes Park, Friern Barnet, Isleworth and Wimbledon took to social media to post videos of the scenes as they expressed their shock at finding whole roads in their neighbourhoods submerged underwater.

Pictures also emerged of people swimming in ponds created by the thunderstorms on Primrose Hill.

In South End Green, firefighters were called to help carry some walkers to safety across roads that had been flooded by water pouring off Hampstead Heath.

And tenants of Lancaster West Estate in North Kensington, near Grenfell Tower, complained that a storm had caused a nearby manhole cover to blow off and 'water and raw sewage' was now flowing around the block.

Elsewhere in the UK, Preston was also affected by flooding, with a section of the M6 having to be closed to traffic for some time on Monday afternoon. It has since reopened.

Yesterday, the Met Office issued a severe rain alert for London after parts of the UK were hit by heavy showers and thunderstorms.

A Met Office spokesperson told Mail Online: 'The torrential downpours could see 20 to 30mm of rain in an hour. Maybe 60mm over two to three hours. Today there is quite a lot of rain around, while tomorrow it becomes a lot more showery.'

The experts issued a yellow weather warning for large swathes of the south coast, with the possibility of flooding to homes, roads and businesses amid the torrential downpours.

A flood warning was also put in place on the River Loddon where river levels have risen as a result of persistent rainfall in previous weeks.

Drivers were told to beware of difficult driving conditions and some road closures due to the heavy rain, while warnings of possible travel disruption across train and bus services were also issued.

The Met Office spokesperson added: 'The yellow warnings covers most of the south coast from Kent down to Devon and up into East Anglia.

'Within that warning area you are at risk of seeing some slow moving heavy showers. There is a chance of some thunderstorms as well. The warning is in place until midnight tonight.'

But other parts of the UK are also set to be damp, even those not covered by the Met Office's official warning.

'Warnings are issued on impact so the warning area is where we are expecting to see the impacts from the rain, but there could still be rain outside those areas,' said the Met Office spokesperson.

'There's heavy showers with the potential for thunderstorms in Northern Ireland and western Scotland as well. It's just that the rain won't have as much of an impact as some of those areas aren't so heavily populated or built.'