The structural design of Waddesdon, however, was not all retrospective. Hidden from view were the most modern innovations of the late 19th century including a steel frame, which took the strain of walls on the upper floors, which consequently permitted the layout of these floors to differ completely from the lower floors. The house also had hot and cold running water in its bathrooms, central heating, and an electric bell system to summon the numerous servants.
Once his château was complete, Baron Ferdinand installed his extensive collections of French 18th-century tapestries, boiseries, furniture and ceramics, English and Dutch paintings and Renaissance works of art. Extensive landscaping was carried out and the gardens enhanced with statuary, pavilions and an aviary. The beautiful Proserpina fountain was brought here at the end of 1800 from the Palace of the Dukies of Parma in northern Italy: the Ducal Palace of Colorno. The grounds were laid out by the French landscape architect Lainé. An attempt was made to transplant fully-grown trees by chloroforming their roots, to limit the shock. While this novel idea was unsuccessful, many very large trees were successfully transplanted, causing the grounds to be such a wonder of their day that, in 1890, Queen Victoria invited herself to view them. The Queen was, however, more impressed by the electric lighting in the house than the wonders of the park. Fascinated by the invention she had not seen before, she is reported to have spent ten minutes switching a newly electrified 18th-century chandelier on and off.
When Baron Ferdinand died in 1898, the house passed to his sister Alice de Rothschild, who further developed the collections. Baron Ferdinand's collection of Renaissance works and a collection of arms were both bequeathed to the British Museum as "The Waddesdon Bequest". During World War II, children under the age of five were evacuated from London and lived at Waddesdon Manor.
Following Alice de Rothschild's death in 1922, the property and collections passed to her great-nephew James A. "Jimmy" de Rothschild of the French branch of the family, who further enriched it with objects from the collections of his late father Baron Edmond James de Rothschild of Paris.
When James de Rothschild died in 1957, he bequeathed Waddesdon Manor, of grounds and its contents to the National Trust, to be preserved for posterity. The Trust also received their largest ever endowment from him: £750,000.
A nearby ancillary property, The Pavilion at Eythrope, had been constructed for Alice de Rothschild by the architect George Devey. This became the home of James de Rothschild's widow, Dorothy de Rothschild, usually known as "Mrs James"; she took a very keen interest in Waddesdon for the remainder of her long life. Eythrope and the rest of the Waddesdon estate remain the property of her heir, the 4th Lord Rothschild.
Jacob Rothschild, 4th Lord Rothschild, has recently been a major benefactor of Waddesdon Manor, and, through the private family charitable trust, has overseen a major restoration, and introduced new collections, thus enhancing the visitor attractions. In an unprecedented arrangement, he has been given authority by the National Trust to run Waddesdon Manor as a semi-independent operation.
In a burglary on 10 June 2003 by the Johnson Gang, approximately 100 priceless French gold snuff boxes and bejewelled trifles were stolen from the collection. None was recovered intact, though fragments of a few were found amid melted gold in the burnt wreckage of a motor vehicle close to the Manor. These artefacts, many encrusted with diamonds, had belonged to, among others, Marie Antoinette and Madame de Pompadour. They were irreplaceable.