Sir Philip Sassoon, 3rd Baronet, GBE, CMG, bought the estate in 1913 with the proceeds of selling his late parents' home Shorncliffe Lodge in Sandgate. His mother was Aline Caroline de Rothschild; his father, Edward Albert Sassoon, was descended from a family of immensely wealthy Iraqi merchants who had moved their banking and trading empire to British India and then to London. Philip was, by inheritance, one of the richest men in Edwardian England. He was also the Conservative MP for Hythe, and his commission to Sir Herbert Baker for the house - originally called Belcaire, then renamed Port Lympne after the nearby Roman port of Portus Lemanis - was Baker's only major country house. Cape Dutch in style, all curved gables and clean white walls, perched on the old sea cliffs above the Marsh. Then the First World War interrupted everything.

When work resumed after the war, Sassoon brought in Philip Tilden, the same architect who handled remodelling work for David Lloyd George and Winston Churchill. Tilden's stated brief was characteristic of his era: "no more of the modest weekend home, but rather the epitome of all things conducive to luxurious relaxation after the strenuousness of war. It was to be a challenge to the world, telling people that a new culture had risen up from the sick-bed of the old." In the early 1920s Tilden added doorcases, the east forecourt, the terraces, and the extraordinary external garden staircase climbing the cliff face. The ground-floor passageway is paved in black and white marble in varying concentric curves, with a barrel-vaulted ceiling above. The staircase is flanked by blue marble columns below and pink above; the iron balustrade is copied from the principal stair at Caroline Park in Scotland. Sassoon called it a moderate house. It had four reception rooms, two libraries, thirteen principal bedrooms, eight bathrooms, and seventeen staff bedrooms with another five bathrooms.

Sassoon's friends were the most fashionable artists of the day, and most of them worked here. Glyn Philpot painted the friezes still on display. Josep Maria Sert - the Catalan artist who set the Ballets Russes for Diaghilev and decorated the Waldorf-Astoria in New York and Rockefeller Center in 1930 - painted the original drawing room in 1914 and 1915 with an Allegory of War in moss-brown and gold, elephants trampling the chimney-piece and a defeathered German eagle. The mosaic work is mostly by Gertrude Martin, who preferred to lay her tesserae on site rather than pre-fabricating them in cement - her work also survives in Belfast Cathedral, the House of Commons, and Westminster Cathedral. Edwin Lutyens and John Singer Sargent both passed through. The garden planting, designed by Norah Lindsay, set herbaceous flowers against dark terraced hedges to evoke an Italian villa. Tilden had also added a bachelor's wing with a Moorish courtyard to accommodate young airmen from the nearby Romney Marsh flying field - Sir Philip was himself an aviator. Lady Honor Channon, never one to soften a remark, called it a Spanish brothel.

August was the month for entertaining. The guest list across the 1920s and 1930s reads like an index to interwar Britain. Charlie Chaplin and T. E. Lawrence. The future Edward VIII and Mrs Simpson. The future George VI. Lord Louis Mountbatten, Lord Curzon, Sassoon's brother-in-law Lord Rocksavage with his sister Sybil. Princess Marthe Bibesco, the prolific Romanian novelist. The novelists Alice Dudeney and Marie Adelaide Belloc Lowndes. George Bernard Shaw, Osbert Sitwell, Giles Lytton Strachey, Sir Harold Nicolson and Vita Sackville-West, Maurice Baring. Sir Douglas Haig and Sir Winston Churchill with Clementine. The former and the future Prime Minister Asquith and Lloyd George. The French politician Alexandre Millerand. The French boxer Georges Carpentier. The composer Ethel Smyth, Philip's own teacher from Eton. The view they shared was from a clifftop above 15.5 acres of gardens cut out of old sea cliffs, with the Marsh stretching out and the Channel beyond.

Sassoon died in 1939, just before the world he had built came apart. The house was bequeathed with its cars and planes to his cousin Hannah Gubbay. In 1942 the RAF commandeered Port Lympne for Free Czech troops, who according to one observer "wreaked havoc on that fastidious connoisseur's 'Rothschild-Levantine' decorations" - and crucially, totally destroyed the Sert elephant paintings in the drawing room, the finest example of 1920s Parisian decorative art in England. Colonel and Mrs Waite bought the abandoned house in 1946. In 1973 the gambler and zoo owner John Aspinall came across it: "a house, a park and a garden that had died suddenly at the outbreak of war in 1939. For thirty-five years the estate had fallen into limbo." He spent a decade restoring it. The great herbaceous border, 135 yards long, was dug over twice by hand and piled with 200 tons of elephant dung from his neighbouring zoo before being replanted with 2,500 herbs and shrubs under the eye of garden designer Russell Page. In June 2014 the Aspinall Foundation opened it as a hotel - four bedrooms and two suites, all named for visitors, creators, or Sir Philip himself - using the revenue to fund wild animal conservation. Whistler's tent room is still painted as it was.