Britain's richest woman Kirsty Bertarelli and her husband Ernesto have left their neighbours 'apoplectic' with plans for their home . Britain's richest woman Kirsty Bertarelli doesn’t usually have to dig deep to get what she wants. When it came to extending the former Miss UK’s London home, however, excavating a vast two-storey subterranean extension seemed the perfect solution. But neighbours in the exclusive street have been left feeling angry – even undermined – by the plan to create a family home for her, husband Ernesto, a Swiss businessman, and their three children. They had raised concerns about the excavation possibly harming the property and adjoining buildings, and about the noise and upheaval caused by the work. Adding to their ire, the council is to restrict such developments by the end of the year because of the disruption they cause – but the Bertarellis got their application in just in time. Planners at Westminster City Council this week approved the application, which will add a dining room, family room and cinema area on one of its levels and a kitchen, gym and laundry area on another. Sketches show this would virtually double the size of the house in Belgravia. Staffordshire-born Mrs Bertarelli, 43, who was 17 when she was Miss UK and also runner-up to Miss World, is the richest woman in Britain, worth nearly £9.75billion thanks to her marriage to Ernesto, 49, a Harvard-educated biotechnology tycoon, according to the Sunday Times Rich List 2014. They bought the Victorian house 15 years ago for £5.5million. Architects Boundary Space said the ‘double decker’ basement is required because the house is no longer big enough for the family, who divide their time between London and homes in Geneva and Gstaad, Switzerland. The upgrade will turn it into a ‘modern family home with appropriate facilities’. Dubbed ‘iceberg homes’, such extensions are the fashionable but controversial solution for rich residents with limited space. The likes of Andrew Lloyd Webber, Nicole Kidman and Roman Abramovich are among those who have all extended underground. According to the architects who designed the project, the 'double decker' basement is required because the house is not big enough for the couple . 'Iceberg' homes have become an increasingly popular way for the rich to expand their homes, without flouting planning restrictions (this image of the house has been altered to protect the owners' privacy) Some homes on the Bertarellis’ mews, one of the most affluent areas of the capital, already have basements, but several neighbours had instructed lawyers to fight the latest proposal. While it will be the third property to have a basement, the Bertarellis would be the first to excavate to two storeys. Staffordshire born Ms Bertarelli, who co-wrote girl band All Saints' worldwide smash Black Coffee, released her own album last year . Locals were also worried that the basement might be used as a recording studio – Mrs Bertarelli co-wrote girl band All Saints’ worldwide smash Black Coffee and released her own album last year – although the plans, approved on Tuesday, show otherwise. One neighbour who wanted to remain anonymous said: ‘Some of the owners around here are absolutely apoplectic about what’s in the pipeline. These kinds of developments cause huge disruption. ‘In the past few years there has already been one double basement conversion and a single basement. There will be hardly any earth left eventually. ‘The houses were never intended to be enormous family homes and the street is just about wide enough to fit two cars down it side-by-side. 'It's like we have rockstars coming to stay when they arrive, there's an army of drivers and minders for the kids, it's mayhem. 'They are obviously going to spend a huge amount on a place they hardly live in, it's staggering. But then the richest are oblivious to how your regular people live and we will have to deal with the consequences.' Another neighbour said: ‘This is going to be a three-year project, they are going to completely gut the building and dig down, I have no idea how that’s going to be done without seriously disrupting us and affecting our day-to-day lives.’ According to the architects who designed the project, the 'double decker' basement is required because the house is not big enough for the couple. The planned upgrade, which will apparently take three years to complete, will turn it into a 'modern family home with appropriate facilities', they said. The architects added: 'The proposals reflect the client's family has grown, and the accommodation is no longer conducive to modern family living.' Ms Bertarelli, 43 (right), who won Miss UK in 1998 (left), bought the house with her husband 13 years ago for £5.5million . In a report considered by the council, it emerged that there had been 'a large number of objections' from residents in the mews, who were concerned the basement may be used as recording studios. The complaints were backed by local Conservative councillor Rachael Robathan, who said: 'The size of the extension is disproportionate.' John Walker, the Wesminster City Council's operational director of development planning said in a report: 'There have been a large number of objections from other residents within the mews. 'Concern has been raised by residents that the use of the basements has not been specified, and that they might be used as recording studios. 'They are concerned that the excavation of new basements is a risky construction process, with potential harm to the property and adjoining buildings.' 'Iceberg' homes became an increasingly popular way for the rich and famous to expand their homes, without flouting planning restrictions. Ms Bertarelli, 43, who won Miss UK in 1998, bought the house with her husband 13 years ago for £5.5million . But the London borough of Kensington and Chelsea became the first local authority in the country to introduce restrictions on the controversial subterranean developments. If the couple lived just a few streets away, their  plans would not have been approved because of the ban on 'excessive' two storey extensions. Westminster City Council is to introduce a similar policy to limit the size of basement extensions by the end of this year. Speaking about the approved plan, council spokesman Nick Thompson said: 'This application was approved by committee on Tuesday night. 'We have a basement policy that is coming in very shortly which will restrict this type of development, as we recognise the disruption that residents in Westminster are having to live with.' Planning permission was granted with conditions that the excavation work can be carried out only between 8am and 6pm Monday to Friday. Nobody was at the Bertarellis’ home for comment yesterday.
Kirsty Bertarelli, 43, is building the basement at her three-storey mansion . Cinema, kitchen and gym will make house conducive to 'modern living'
Neighbours have been left 'apoplectic' over the plans for 'iceberg home'
She and husband Ernesto will be first home on road to excavate two floors . Westminster council is banning 'iceberg' developments at end of this year .