British conservation charity the National Trust has announced that architecture practice Allies and Morrison will reimagine and rebuild Surrey’s Clandon Park, a historic Palladian mansion gutted by a fire in 2015.

The firm was selected ahead of five other rivals in an international design competition, organised by Malcolm Reading Consultants.

However, in an unusual move, one of the other shortlisted practices, Purcell, has joined the winning ticket as conservation architect.

Clandon Park was designed by Venetian architect Giacomo Leoni in the early 18th century for a local baron, and became celebrated for its double-height Marble Hall, with a sculptural plaster ceiling by stuccadore Giuseppe Artari.

While the brickwork exterior largely survived the blaze and approximately 500 objects from the collection were rescued, the debris inside reached 8ft (2.43m) high. Some of the historic decorative plaster and building fabric has been carefully excavated and saved.

The search for a multidisciplinary team to restore the Grade I-listed building was launched in March 2017 and 60 teams submitted designs for the reimagined building, which will include galleries, a visitor centre, a cafe and retail space.

The jury – including V&A Museum design director David Bickle, architectural historian Clive Aslet, and actor and local resident Penelope Keith – were unanimously in favour of the Allies and Morrison proposal, which they praised for its “bold yet balanced approach to respect the quality and character of the mansion house in its historic setting” with an “appropriate level of drama and excitement”.

Describing the design approach, Allies and Morrison partner Paul Appleton said: “It’s about balance; meticulously reinstating historically significant spaces while in others exploiting the extraordinary character of massive brick walls.

“New floors and ceilings are slotted into this robust matrix to re-order and to redefine, but only just as much as is needed to create timeless spaces without erasing the marks of time.

"From a restored Marble Hall, through the series of grand rooms on the principal floor, to a soaring new space connecting the lower ground floor to a new roof-terrace, each element plays its own particular part.

“It’s hard to imagine an architectural project which bears more directly on the question of how we respond to our heritage. We feel enormously privileged to work with the National Trust to unfold the story Clandon Park has to tell and to begin, together, to weave plans for its future around the extraordinary evidence of its past.”

The firm has previously worked on projects in the heritage sector including the refurbishment of Royal Festival Hall and the insertion of a new planetarium at the Royal Observatory in Greenwich, both in London.

On the Clandon Park project, they will collaborate with structural engineer Price & Myers and services engineer Max Fordham. A landscape architect will be appointed after further consultation with the National Trust.

The next stage of the project includes a detailed feasibility study and consultation process.