Harry Benjamin Inigo Triggs was born in Chiswick, London, on 28 February 1876, to parents James Triggs, carpet agent, and his wife Celia Anne, née Bryant. His older brother was Arthur Bryant Triggs (1868–1936) born in Chelsea, who in 1887 emigrated to Australia, becoming a wealthy New South Wales grazier (known as The Sheep King) and collector of art, books and coins. The architect Inigo Jones was a distant relative. 1907 he married Gladys Claire.
In 1910 Triggs bought the property then called Fry's Farm, in Liphook, Hampshire. He re-designed the farmhouse and gardens as his home, and renamed it Little Boarhunt, based on a legend about King John hunting boar in the district. The house is now a Grade II listed building, being a representative romantic house of the Arts and Crafts Movement.
Triggs designed many formal gardens and later some country houses, mostly in southern England. He specialised in historical research and in re-creating gardens of the past. His books influenced the Italian mode of the Arts and Crafts style in England. He also designed Cooper's Bridge at Bramshott and the War Memorial in Petersfield High Street in 1922.
In 1906 he was awarded the Godwin Bursary, presenting two reports: "The planning of public squares and open spaces" (76 pages), relating to the cities of Paris, Berlin, Vienna and Munich, including public monuments and fountains; "Le Petit Palais, Paris" (20 pages), a detailed description of the Musée des Beaux-Arts building, Avenue Winston Churchill, designed by Charles Girault and built between 1897 and 1900.
In the 1910s Triggs was in partnership with the architect William Frederick Unsworth (1851–1912), and his son Gerald Unsworth (1883–1946), in Petersfield, Hampshire. W. F. Unsworth had previously designed the Shakespeare Memorial Theatre in Stratford-upon-Avon in 1879, which was destroyed by fire in 1926 and replaced in 1932 with the present Royal Shakespeare Theatre.
In the summer of 1919, Mr Inigo Triggs, well-known to the Trustees of The Whiteley Homes Trust Ltd, was engaged to plan and supervise the landscaping of the area surrounding the cottages of Whiteley Village, Walton on Thames, Surrey. The principle being that the four main roads at right angles to the central feature of the Monument, be called Avenues and the transverse ways bisecting these quadrants to be called Walks. All four of the Walks were turfed and this turfing was continued into the areas between the Walks and the Monument within Circle Road. The remaining unturfed areas within the circle were edged with heather, and existing trees and shrubs were left in place. The entire length of the Avenues were lined with trees, which continued in front of the cottages, with Scotch Pines being used along the North and South Avenues and Lime Trees along East and West Avenues. The other areas were designed separately and included the use of Fruiting Trees and Shrubs and Lavender borders.
- Little Boarhunt House and gardens, Liphook, Hampshire (1910) including a sunken Elizabethan garden.
- The Rectory Liphook, Hampshire (1912)
- Rookswood's Windrush Lodge Nazeing, Essex (1913)
- Homefield Nazeing, Essex
- Barrow Court, Somerset (1890)
- Saighton Grange (now Abbey Gate College) Cheshire (1901)
- Chillington Hall, Staffordshire (1911)
- Ashford Chace, near Petersfield, Hampshire, for Aubyn Trevor-Battye (1912) (photo of Ashford Chace).
- Some Architectural Works of Inigo Jones (1901) A series of measured drawings and other illustrations together with descriptive notes; a biographical sketch and list of his authentic works, B T Batsford publishing. With Henry Tanner.
- Formal Gardens in England and Scotland (1902) Their Planning And Arrangement, Architectural And Ornamental Features, B T Batsford publishing, 63 pages. Republished 1988.
- The Art of Garden Design in Italy (1906) Longmans publishing, 135 pages. Republished 1942 and 2007.
- Town Planning, Past, Present and Possible (1909) with 173 illustrations, Methuen & Co, 334 pages. Second edition (1911).
- Garden Craft in Europe (1913) C Scribner's Sons publishing, 332 pages. Republished 1933 and 2008.
- RIBA Journal, 1923, volume 30, page 431 – Obituary.
- Country life, 1995, volume 189, number 43, 26 Oct, pages 58–61 -"Designs for a garden – formal informality" by Diana Baskervyle-Glegg, on Triggs' Edwardian garden designs.
- The Whiteley Homes Trust, by Alan Brown 1992 ISBN 0 85033 847 2
- Parks and Gardens UK – Harry Inigo Triggs summary record
- Plans and drawings by Harry Inigo Triggs (Bridgeman Art Library – 1 September 2010)