How on earth, you cannot help wondering, can anyone live like this?
The obvious question misses the point, which is that this is not a home that sacrifices lifestyle for design. Rather, the reverse is true. The flat has been designed as a base from which its occupants can venture out, not as a home to potter in. "As Australians living in Europe, we're very conscious that there are a lot of things to see and do," explains Genevieve. "We both like doing things and tend to use our weekends as opportunities to explore, whether here or abroad."
The couple collaborated on the design, although Genevieve is the architect by profession. Aged 32, she has recently left David Chipperfield Architects after seven years to set up a practice on her own, and is currently working from home. With enough work to be able to pick and choose her projects, her decision to leave one of the most respected practices in Europe appears to have been the right one.
The only person to have been compromised by her decision is her husband, Kingsley Wallman, a corporate lawyer for a large telecommunications company. "He has had to adapt to the extra mess at home," she says, gesturing towards an orderly pile of sleek files by the windows, "but he sees the need to keep overheads low, and so he tolerates it."
Genevieve and Kingsley were as clear about the kind of flat they wanted as they were about what its interior should be like. "We knew we wanted a garden square, so we could have a green outlook in an urban context," says Genevieve, "and we needed to be near central London because of our work." So they mail-shot their preferred area - Bayswater - targeting the buildings which looked suitable. They received some replies and finally bought the flat in 1995.
As conversions go, the first-floor flat is ideal. The imposing stucco-fronted building has been carved up neatly into flats (one per floor), the ceilings are high and the architectural features lavish. A balcony overlooks the leafy square, compensating for the grim car park to the rear.
Genevieve and Kingsley approached the task of renovation with the same precision she would bring to any professional project. Together they constructed a 3D model, even though both were aware that there are "only so many things you can do with such a limited space".
Luckily, no conflicts arose. "We share very similar tastes in architecture," says Kingsley. "I am influenced by Genevieve, but I was brought up in a Modernist Sixties' house in Australia and have always been interested in buildings."
It was Kingsley who demolished the labyrinth of tiny rooms to reveal a simple L-shaped space. The large area is painted white, and has floors of bleached oak. The bathroom, which is housed in a painted blue box in the middle of the room, has a glass lid which rests a metre below the ceiling. This allows light to flow inside the box, creating an illusion of space while shutting out noise. Two outside walls of the blue box are lined with cupboards, and the inside is clad with putty-coloured slabs of cool limestone. "Bathrooms are extremely underrated," Genevieve explains. "After all, you start and end your day in them. Stone makes a bathroom luxurious." There are no doors separating the living area from the sleeping quarters, which are on the other side of the bathroom.
By the time it came to furnishing, money was a bit tight, though you wouldn't know it to look at the flat. "Whether you are designing a six- bedroom house or a studio flat, the problems are the same," says Genevieve. "Most of the money disappears into the infrastructure of a building, where you can't really see it. I would have loved to have a recycled mahogany table for example, but in the end we could only afford this orange painted door as a table top." Other bits and pieces were salvaged from unlikely places: the bathroom taps, for instance, were spares from the "strip-out" of a Soho restaurant site.
"We wrestled for a while with the kitchen, but eventually decided to place it where it had always been, in one corner of the sitting-room," says Kingsley. Enormous cupboards made of MDF and sprayed white stretch up to the 14ft-high ceilings. The cupboards house the fridge, crockery and food. A stainless steel counter holds the remaining culinary equipment. There isn't a crumb-trailing toaster or unsightly washing-up glove in sight. "I have learnt to be disciplined in what and how I cook for friends," Genevieve says.
In the living space, a suspended concrete shelf slides under the "hole- in-the-wall" fireplace and fulfils the joint functions of shelf, coffee table and mantelpiece. "The criteria for that shelf was that it should be able to support the weight of 10 adults dancing on it. And it does," Genevieve laughs, referring to their wedding night, when 50 friends were invited back to the flat to celebrate.
Genevieve is the first to acknowledge the sparseness of their home, but, she says, the way it looks is an honest reflection of their lifestyles. Her wardrobe is frugal because she is "not a great shopper"; there are no novels about because they always give them away to friends once they have read them.
"I can see that the flat isn't suitable for a couple where one person likes listening to music and the other person prefers to watch television. But it works very well for a couple who enjoy each other's company." She taps a blue cupboard door behind her. "We were given a TV by some friends, but as we have nowhere to put it, we never get it out. We probably watch it about twice a year."
Almost as remarkable as their home is the fact that two such meticulous souls could have found each other at all. "I don't think that I ever expected to meet anyone, because I am so self-centred and self-absorbed," Genevieve admits. "It is good that I met someone who is equally ego- centric, and running in roughly the same direction as me. Although we are not similar on a lot of levels, we like doing a lot of similar things."
Ironically, the two met in Britain, despite their shared Antipodean roots. "It's depressing to think that I travelled half-way around the world to meet another Australian," she jokes. Both are from large "loopy" families, and both are driven by a strong sense of purpose and a quest for perfection. "I think coming from a reasonably large family encourages you to be tolerant" - an essential quality when cohabiting in so confined a space.
Of the two, Kingsley is the tidier. "His whole family are obsessively neat," says Genevieve. And although both are clearly extremely motivated, it is Kingsley who appears to dominate their recreational time: "He has got a programme for every minute of the weekend. What we are doing and where we are going. He can't sit around at all." Their early morning routine, which Genevieve describes as being "a bit like school camp", involves getting up at 7am either to swim or run.
Hearing all this, it gradually becomes easier to understand why their sofa doesn't need to be the "sort of sofa that you would fall asleep on, on a Saturday afternoon". Rather, you understand why its aesthetic qualities and harmonious relationship with the interior space are fundamental to such orderly minds.
In spite of appearances, it would be wrong to describe Genevieve and Kingsley as minimalists: "I hate the word minimalist," Genevieve grimaces. "It has become such a cliche." They may not own much, but this is for the simple reason that they don't need much. "I am not averse to possessions," says Genevieve. "Part of the fun of working with clients is working with their belongings - making a photo wall if they have a lot of photos, making a book wall if they have a lot of books."
So how do they keep this flat - probably one of the tiniest, tidiest flats in London - looking so immaculate?
They pay for a cleaner, of course.