Grand Designs - House of the Year: 'invisible' hillside retreat and a modernist Sixties house are the first two homes shortlisted for Riba prize

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 have been announced as the first two houses to be shortlisted for the coveted 2016 RIBA House of the Year award.

Host Kevin McCloud and Riba judges Damion Burrows and Zac Monro picked the spectacular projects from five houses that were featured on the first 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.

Outhouse, in the Forest of Dean, is a vast property built on an architectural conceit, creating three courtyards where rundown farm buildings, including a pig sty, once were, while the house's 150ft corridor stands on the route of the old farm track.

Architect Meredith Bowles, a member of the Riba judging panel, reveals the reasons it was picked for the shortlist.

Praising "the strength of its idea", Bowles says: "It's almost like a house as a city, it's got a number of parts to it, it's got a street down the middle."

Of putting Ansty Plum on the list, Bowles says: "This is a very intelligent refurbishment, it's a celebration of restraint. This was not a big grand project, it was taking away almost as much as it was putting in."

The Wiltshire home, built in 1962, was falling apart when Sandra Coppin bought it and began a bare-bones refurbishment to exacting standards.

Bowles says: "It's suggesting that to make a house that is for today needn't be much different to a house from 50 or 60 years ago.

"We don't need lots of grand bathrooms, we don't need much more than the simple house it originally was."

Grand Designs: House of the Year is on Thursdays on Channel 4 at 9pm