A white, mirrored house half buried in a plot in a conservation area in Clapham and a Wallace and Gromit-style palace of gadgets in Edinburgh have been announced as the second two houses shortlisted for the coveted 2016 Riba House of the Year award.
Host Kevin McCloud and Riba judges picked the properties from five experimental houses featured on the second episode of a special series of Grand Designs programmes for Channel 4.
The prize, run by the Royal Institute of British Architects, is awarded to the best new house designed by an architect in the UK.
Covert House was created in the grounds of a period home which architects David Hills and Deborah Saunt bought and sold on, keeping the garden for themselves.
Digging 16ft down to create a basement with three south-facing bedrooms illuminated by a double-side light trough, the main living and dining area is on the first floor and the above ground external walls are edged in mirrors to make it even more invisible to the neighbours.
Riba judge Charlotte Skene Catling says of the Covert House: "It appears as a very tiny, jewel-like object sitting within the middle of the site and then it unfolds, and then there's a treatment of external surfaces so it disappears."
The Riba judges also put Murphy House on the shortlist, and Catling says: "It responds to its context in an incredibly complex way. it's an extraordinary thing."
Richard Murphy created the 1,800sq ft home, on no less than eight levels, in a plot 36ft by 20ft, the size of a small one-bedroom flat.
Automatic shutters, a bedroom with a hidden bath, walls that fold out and a bookcase with secret window panels all delighted the judges.
After revealing the pair of houses on the shortlist, Grand Designs presenter Kevin McCloud says: "Employ the right architect and you get a super-engineered, sleek, timeless slice of beauty, whatever your budget."
They join a Sixties modernist house 'brought back from the dead' in rural Wiltshire and a partly-subterranean concrete retreat carved from a sloping plot in the Forest of Dean, that were annound as the first two houses to be shortlisted, last week.
Grand Designs: House of the Year is on Thursdays on Channel 4 at 9pm