Buried in the seclusion of the densely wooded Fowey valley, and surrounded by hundreds of acres of parkland, Lanhydrock is eventually sighted after a good downhill walk through the grounds from the car park. Looking every inch like a solid, Victorian mansion, the highly decorative mid-17th century gatehouse provides the first clue that all is not quite what it appears to be.

In 1620 Sir Richard Robartes, the son of a hugely successful Cornish moneylender, bought the old monastic manor at Lanhydrock, and began to build a traditional four-sided house around a central courtyard. After his death in 1634, the house was completed by Robartes' son, John, a sullen and difficult man by all accounts, who was a prominent Parliamentarian during the Civil War. For the next 335 years, many of the successive owners of Lanhydrock became MPs, and took an active interest in local affairs.

Little change was made to the house over the next two centuries, apart from the demolition of the east range in the 1780s, and the house gradually lapsed into a state of disrepair. Remaining unoccupied for long periods of time, it suffered greatly from neglect, and it was practically empty of its contents. When, in the mid-19th century, the 1st Baron Robartes of Lanhydrock and Truro came to live at his ancestral home, he commissioned George Gilbert Scott to modernise and remodel Lanhydrock. This Victorian architect, one of the most renowned for his extensive restoration works on medieval cathedrals, attempted to reinstate Lanhydrock as a comfortable country house.

Just 20 years after the work had been completed, fire destroyed all but the north wing of the house, and the shock of this disaster killed Lady Robartes a few days later. Distraught at losing both his wife and his home, Lord Robartes died the following year. Their son, Thomas, had the house re-built with a neo-Jacobean façade, but a traditional Victorian arrangement of rooms internally. This work was undertaken by a local architect, Richard Coad, who was a former pupil of Scott's and had previous experience of Lanhydrock during the earlier modernisation programme. To enable Coad to incorporate the required separation of family and servants dictated by Victorian principles, it was necessary for him to build a whole new complex adjoining the existing southern range of the house.

When the house was presented to the National Trust in 1953, it came with few contents, and much of the current furniture represents a similar arrangement to what would have been in use after Coad's rebuilding of Lanhydrock. By far the most impressive room in the house is the gallery. Situated in the north wing, it fortunately survived the devastating fire of 1881, and the exquisitely carved plasterwork ceiling is of outstanding quality. Among the large collection of books is one of the four volumes of the Lanhydrock Atlas, a survey of Charles Bodville Robartes' (the 2nd Earl of Radnor) estates in Cornwall at the end of the 17th century, showing 40,000 acres on 258 manuscript maps. It was through his marriage that the family also acquired Wimpole Hall near Cambridge, and most of the contents of the drawing room came from that stately mansion. Many family portraits adorn the walls of the house but little else can be personally attributable to the Robartes.