It's no secret that London is becoming one of the most expensive cities in the world. As a matter of fact, London's rental prices are so steep, more and more "middle class folk" are venturing to the outskirts of London, while only the rich and famous remain in its city center.

If you want to explore London's richest neighbourhoods, or even stalk a celebrity or two, here are the neighbourhoods in London which are known to house some of the richest and famous residents in London:

Knightsbridge

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Photo credit: Rob Deutscher

Knightsbridge is popular among London's celebrities for one reason and one reason only: Number One Hyde Park. This address is known to be the most expensive piece of private real estate in the UK, and each flat costs approximately $11,000 per square foot. Residents at this address can enjoy a stainless steel ozone pool, cinema, wine cellar, a valet service, and even a panic room, and the building was developed by the Candy Brothers and the Prime Minister of Qatar (who paid $64 million for his own triplex at the address). Other famous residents at this address include Kylie Minogue, as well as Vladimir Kim (the wealthiest man in Kazakhstan).

What to do in Knightsbridge: Take an afternoon stroll around Hyde Park, window shop at Harrods, visit the Victoria and Albert Museum

Richmond

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Photo credit: Hans Dinkelberg

Call it coincidence that some of the richest people in London call Richmond their home; (as a matter of fact, Richmond has more wealthy residents than any other London borough!) The area is popular among London's celebrities as it has a ton of green space and is very family-friendly, and the average cost of a two-bedroom flat is around £300,000. Two members of The Rolling Stones live here (Sir Mick Jagger and Ronnie Wood), as well as Pete Townshend (The Who), Brian May (Queen), actress Keira Knightley (Pirates of the Caribbean), and even Brad Pitt and Angelina Jolie.

What to do in Richmond: Visit the Kew Palace/Kew Gardens, check out rich people's homes on Richmond Hill, go deer spotting

Chelsea and Kensington

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Photo credit: George Rex

Chelsea and Kensington have always been the most luxurious of London's neighbourhoods, so it doesn't take a rocket scientist to see why so many celebrities live here. As a matter of fact, some of the homes in these neighbourhoods can cost anywhere from £1.7 million to £30 million pounds, and the block of Kensington 8 (where Madonna lives), boasts a private museum for vintage ferraris, underground swimming pools and private cinemas. Some of the other famous Chelsea and Kensington residents include Formula 1 mogul Bernie Ecclestone, John Fredriksen (Norway's richest man), and David and Victoria Beckham.

What to do in Chelsea and Kensington: Go window shopping at some high-end boutiques, party with the Chelsea football team at Bijous nightclub, check out the expensive yachts at Chelsea Harbour

Notting Hill

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Photo credit: Ryan Finn

Notting Hill may not be as loaded with celebrity homes as much as the other neighbourhoods in London, but it's known to be a popular shopping area for the rich and famous in London. Celebrities are drawn to Notting Hill because of its world-famous markets and vintage shops, and celebrities in London are often spotted here while they do some hardcore shopping; (because celebrities in London are people too, you know!) Some of the many celebrities who have been spotted here over the years include Stella McCartney (daughter of Sir Paul McCartney), X-Factor's Simon Cowell, singers Elton John and Robbie Williams, and Blur's Damon Albarn.

What to do in Notting Hill: Window shop along Portobello Road, check out some vintage clothing shops, try some street food at Portobello Market

Primrose Hill

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Photo credit: diamond geezer

During the 1990s, Primrose Hill became famous for the group of London celebrities who resided here (now known as "The Primrose Hill Set"). Some of these celebrities included Liam and Noel Gallagher of Oasis, Kate Moss, Jude Law and many more. But since then more and more celebrities in London are flocking here, and are often spotted at gastropubs and cafes along Regent's Park Road and Gloucester Avenue. Some of Primrose Hill's most recent celebrity residents include Daniel Craig, Harry Styles, model Suki Waterhouse and even Stefano Gabbana (of Dolce & Gabbana).

What to do in Primrose Hill: Fly a kite in Regent's Park, have a picnic and watch the sunset at Primrose Hill park

Clapham

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Photo credit: PROstevekeiretsu

Clapham is especially popular among London's richest entrepreneurs, as well as playwrights, hedge-funders, or Londoners with a lot of "new money," many of which hang their hat in the mansion blocks along Clapham Common. But Clapham is also a popular party neighbourhood for celebrities in London as well (Ashley Cole was recently spotted partying it up at Aquum). Some of the most well-known Clapham residents include Piers Morgan, Heather Mills (ex-wife of Sir Paul McCartney), Harry Potter author JK Rowling, and Sarah Ferguson.

What to do in Clapham: Take a walk through Clapham Common, buy some local produce at the Venn Street Market, party it up at Infernos nightclub

St. John's Wood

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Photo credit: trasdun

Not only is St. John's Wood home to Abbey Road and the most famous recording studio in rock and roll history (Abbey Road Studios), it's also packed full of a ton of celebrity homes as well; (with Avenue Road and Tufnell Park being especially popular among London's rich and famous). Actor Damian Lewis (Homeland, Band of Brothers) and Bill Nighy live here, as well as Sir Paul McCartney, model Kate Moss, Keith Richards (of The Rolling Stones) and Scottish actor Ewan McGregor. Tom Cruise was even spotted looking at homes in the St. John's Wood area, and comedian Mel Smith lived in St. John's Wood until his death as well.

What to do in St. John's Wood: Walk across Abbey Road, visit Abbey Road Studios, buy some Beatles souvenirs at the Underground station, admire the mansions along Avenue Road