Five experimental houses are the stars of the second in a special set of Grand Designs programmes leading up to the coveted Royal Institute of British Architects' House of the Year prize, to be awarded next month.
In tonight's programme, Grand Designs presenter Kevin McCloud says that the longlisted selection reflected the Riba judges' search for homes "that provided solutions for living with creativity and flair".
1. MIRRORED JEWEL OF SUBURBIA
Covert House, Clapham (pictured above)
Kevin says of the first house on the long list that it almost seems impossible that such a house could exist in a conservation area.
He adds: "It is a military, covert operation in architecture: it digs underground to maximise space and camouflages itself with mirrors to reflect back its surroundings."
Architects David Hills and Deborah Saunt went about building their dream home by buying a period house and selling it, but hanging on to the overgrown garden.
It took them four years, a planning appeal and assuaging the worries of 23 neighbours, but they managed to build a substantial family home that is almost invisible thanks to digging 16 feet deep and the mirrored edges of the exterior walls above ground.
The 1,400sq ft building was designed to an upside-down layout, with the kitchen, dining and living room on the first floor, while three bedrooms, two bathrooms and another living area are in the basement.
That floor is lit by a light trough on two sides and all three bedrooms face south to make the most of the light.
Deborah says: "We had to dig, dig, dig. It's almost like a Georgian trick - they had houses with basements, so they had houses with steps up to the main entrance to allow the light to come in."
Although they kept to just three design concepts - concrete, white and glass - the couple wanted a home that felt comfortable, as Deborah says: "The idea is that you can feel how the building was crafted, so it's not like one of these CGI experiences."
2. WALLACE AND GROMIT BOX OF TRICKS
Murphy House, Edinburgh
Kevin says that this house was one of the most surprising in this year's House of the Year competition, conjuring 1,800sq ft of living space from a plot just 20ft wide by 36ft deep.
He adds: "Around every corner, up every stair, there is a new surprise in this complex treasure chest of a house."
Set in the heart of historic Edinburgh, architect Richard Murphy spent nine years designing and building his home which is set over no less than eight levels.
In the basement, a bedroom shares space with the utility room, upstairs is one more bedroom and a garage, on the next level is a study, while spread over several levels are a living-dining-kitchen, as well as a garden terrace.
The crowning glory of the house is the master bedroom, which doesn't have an en suite bathroom because the bath is inside the bedroom - beneath the lid of a wooden bench.
Above the bath, two thick wooden shutters open a whole corner of the building, allowing Richard to indulge in al fresco - albeit, not so private - bathing in his bedroom.
This amusing find sums up the house, which is full of Richard's gadgets, ostensibly to be more eco-friendly, but he admits, also for fun and also includes bookcase with secret panels that turn into windows.
Every major window is fitted with insulated shutters that slide or pivot to allow the glass to generate heat during summer, while keeping the house cosy in the long Scottish winters.
Richard tells Riba judge Damion Burrows on his visit: "Curtains are not very solid, and I don't like them anyway - you want to have a real cocoon and also it's a piece of fun."
Kevin concludes that the house is "an ingenious and playful nest, constructed by a wise old owl".
3. MEMORIES AND HISTORY BUILT IN
House of Trace, Forest Hill, London
From the front, this home looks like nothing more than a very clean example of a Victorian end-of-terrace house.
Around the back, however, it is easy to see why what some might see as a mere extension has transformed the property into something amazing.
The Japanese owners employed fellow Japanese architect Taro Tsuruta to turn the two-up, two-down house into one fit for a family of four, on a budget of £247,000.
Tsuruta decided not to just stick a modern extension on the back of the house, but to incorporate the Victorian home into the fabric of his design.
The 1,200sq ft extension is notable not for its airy downstairs kitchen-diner and bathroom and bright upstairs master bedroom, but for the way it keeps a note of the building's history throughout.
Tsuruta designed all the furniture and cabinets on his computer, emailed them to a CNC company that produced flatpack kits which were returned within the week.
The parts were assembled like a jigsaw puzzle, and the part numbers to guide the builders are still visible around the house, reflecting the traces of the house's former shape revealed in the wall outside.
Tsuruta reveals that one reason he made the most of showing to people what had happened to the house over its century-long existence was that his memory had become very important in his life because his mother has Alzheimer's disease.
Kevin concludes that the house provides "persistent reminders of the importance of making and how we make sense of our world".
He adds: "We are creatures motivated by memory, nostalgia and the imagination - things which great buildings like this provide in spades."
4. MODERN MASTERPIECE, HISTORIC TOWN
Private House, Cumbria
Owners Sue and David commissioned this house from friend and architect Rab Bennett after discovering the joys of living in a modern home when they spent several years working in Abu Dhabi.
When they returned to Britain, they no longer wanted to live in their centuries-old mill house and decided to build a 4,100sq ft, four-bedroom home in the heart of a medieval market town in Cumbria.
Although the plot had existing planning permission, its granting had been very unpopular in the town and Rab says he took great pains not to upset the neighbours with his design.
Riba judge Zac Monro discovered a two-winged property, one with a living room, two bedrooms and a terrace, the other wing with a kitchen-diner, two further bedrooms, a workshop and a garage.
This house is all about the views. Sue and David's splendid views across a valley are provided by vast picture windows, while lights flood inside the house from a glazed atrium.
Zac concludes that the house shows "an immense amount of consideration for the landscape and local people".
5. METROLAND SUN TRAP
House 19, Amersham, Buckinghamshire
The last house in the experimental homes longlist looks traditional from the outside, but on the inside has "impeccable green credentials", says Kevin.
Apart from ingenious window vents, preheating ground air ducts and automatic ventilation, the 2,600sq ft property is all about catching the light, with its solar-panel covered roof facing south, a sun trap courtyard and a double-height light well.
Architect Heinz Richardson spent years studying the site by living in the old house that once stood there, before deciding what to build and Kevin says: "Every corner, every shaft of light seems mature and considered."
The judges praised the house's simple, sustainable design, its inspiring series of rooms and, of course, its superb management of light.
Kevin concludes: "The house is parsimonious with the earth's resources, generous with its neighbours and reinvigorates life in Metroland."
Grand Designs: House of the Year is on Channel 4 on Thursdays at 9pm
Of the five houses detailed here, two will be placed on the Riba House of the Year shortlist and their names will be announced at the end of the show