The estate was technologically advanced; the architect of the house, Richard Norman Shaw, wrote that it was equipped with "wonderful hydraulic machines that do all sorts of things".

[2] In the grounds, Armstrong built dams and lakes to power a sawmill, a water-powered laundry, early versions of a dishwasher and a dumb waiter, a hydraulic lift and a hydroelectric rotisserie.

In 1910, the best of Armstrong's art collection was sold off, and by the 1970s, in an attempt to meet inheritance tax, plans were submitted for large-scale residential development of the estate.

[7][8] He established himself as a figure of national standing: his work supplying artillery to the British Army was seen as an important response to the failures of Britain's forces during the Crimean War.

[16] Salvin had taught him the mastery of internal planning which was essential for the design of the large and highly variegated houses which the Victorian wealthy craved.

[22] The architectural historian Andrew Saint records that Shaw sketched out the whole design for the "future fairy palace" in a single afternoon, while Armstrong and his guests were out on a shooting party.

Both were sold in the 1910 sale; Chill October is now in the private collection of Andrew Lloyd Webber,[27] and Jephthah's Daughter is held by the National Museum Cardiff.

The architectural writer Simon Jenkins records: "Japanese, Persian, Siamese and German dignitaries paid court to the man who equipped their armies and built their navies".

Armstrong's biographer Henrietta Heald mentions two future prime ministers of Japan, Katō Takaaki and Saitō Makoto, among a steady stream of Japanese industrialists, naval officers, politicians and royalty who inscribed their names in the Cragside visitors' book.

[34] In August 1884 the Prince and Princess of Wales (the future Edward VII and Queen Alexandra) made a three-day visit to Cragside; it was the peak of Armstrong's social career.

The royal arrival at the house was illuminated by ten thousand lamps and a vast array of Chinese lanterns hung in the trees on the estate; fireworks were launched from six balloons, and a great bonfire was lit on the Simonside Hills.

[35] On the second day of their visit, the Prince and Princess travelled to Newcastle, to formally open the grounds of Armstrong's old house, Jesmond Dean, which he had by then donated to the city as a public park.

[43] Watson-Armstrong lacked Armstrong's commercial acumen and a series of poor financial investments led to the sale of much of the great art collection in 1910.

[49] The experiments had led to the publication in 1897 of Armstrong's last work, Electrical Movement in Air and Water, illustrated with remarkable early photographs by his friend John Worsnop.

[51] Cragside is an example of Shaw's Tudor revival style;[14] the Pevsner Architectural Guide for Northumberland called it "the most dramatic Victorian mansion in the North of England".

[56] The architectural historian J. Mordaunt Crook considers Cragside to be one of the very few country houses built by the Victorian commercial plutocracy that was truly "avant-garde or trend-setting".

[57] In his study, The Rise of the Nouveaux Riches, Crook contends that many new-monied owners were too domineering, and generally chose second-rate architects, as these tended to be more "pliant", allowing the clients to get their own way, rather than those of the first rank such as Shaw.

[62] The architectural historian Jill Franklin notes that the vertiginous fall of the site is so steep that the drawing room, on a level with the first-floor landing at the front of the house, meets the rock face at the back.

[65] The architectural correspondent of The Times, Marcus Binney, who was closely involved in the campaign to bring Cragside to the National Trust, noted the historic importance of this "virtually untouched interior",[66] with its collections of furnishings, furniture (much designed especially for Cragside), and fine and decorative arts, with work by many notable designers of the period, including William Morris, Dante Gabriel Rossetti, Philip Webb and Edward Burne-Jones.

[69] For the visit of Edward and Alexandra, Armstrong brought in the Royal caterers, Gunters, who used the kitchen to prepare an eight-course menu which included oysters, turtle soup, stuffed turbot, venison, grouse, peaches in maraschino jelly and brown bread ice cream.

[14] The writer Michael Hall suggests that the bath, with its plunge pool, was intended as much to demonstrate Armstrong's copious water supply as for actual use.

[17] As was often the case, Armstrong also found practical application for his pleasures: steam generated while warming dry air for the Turkish bath supported the provision of heating for the house.

[77][d] A portrait of Armstrong by Henry Hetherington Emmerson shows him sitting in the inglenook with his dogs,[83] under a carved inscription on the mantlepiece reading East or West, Hame's Best.

[85] Other bedrooms, notably the Yellow and White rooms, were hung with wallpaper by William Morris, including early versions of his Fruit and Bird and Trellis designs.

[90] Lighting, and his means of providing it, mattered to Armstrong, on both technical and aesthetic levels; he wrote, "in the passageways and stairs the lamps are used without shades and present a most beautiful and star-like appearance.

[94] Jenkins considers it "surely the world's biggest inglenook" and describes the overall impact of the room as "sensational", noting the top-lit ceiling and the elaborate Jacobethan plasterwork.

[31] Others have been less complimentary; the writer Reginald Turnor, no admirer either of Shaw or of Victorian architecture and its architects more generally,[95] wrote of the room's "flamboyant and rather sickening detail".

[92] By the time of its construction, Shaw, increasingly working for clients of great wealth, had moved on from his "Old English" style,[96] and the room is designed and decorated in a grander and more opulent Renaissance taste.

[111] A plaque at Bamburgh Castle, Armstrong's other residence on the Northumbrian coast, records that his development of these new automated technologies "emancipated ... much of the world from household drudgery".

[45] The glen north-west of the house is spanned by an iron bridge, crossing the Debdon Burn, constructed to Armstrong's design[120] at his Elswick Works in the 1870s.