From Graces Guide
J. I. Thornycroft and Co, of Smith Square, London, Chiswick, Basingstoke and Southampton, boat builders, engine makers, vehicle builders.
See also -
1864 John Isaac Thornycroft, naval engineer, commenced building steam driven launches at Chiswick.
1866 John I. Thornycroft and Co founded.
1894 Read a review of the Works in The Engineer 1894/02/23.
1894 Details of a Rapid Rock Drill made by them for Richard Schram and Co
1899 Thornycroft's partner, John Donaldson, died.
By late 1899 William Beardmore had joined a syndicate that bought the torpedo boat builders J. I. Thornycroft and Co of Chiswick; Beardmore was subsequently appointed chairman.
1901 Public company. The company was registered on 22 May, to acquire the business of builders of torpedo boats, of the firm of the same name.
1901 Became a public company John I. Thornycroft and Co. Ltd, to bring in extra capital. The funds were chiefly provided by William Beardmore who hoped to make the shipbuilding firm a tied customer for his iron and steel and to expand the infant Scottish motor industry but these hopes were not fulfilled.
1901 Joint venture: Thornycroft-Marshall Boiler
1902 Built their first petrol-engine vehicle.
By 1904 Beardmore had lost interest in Thornycroft's company and from then on the firm was largely run by Thornycroft's eldest son, John Edward, who oversaw the removal of the shipyard from Chiswick to Woolston in Southampton, a move made necessary by the increasing size of torpedo boats and destroyers.
From then on, the vehicle building side and the marine side (later to become Vosper Thornycroft) were separate companies.
1907 Beardmore resigned as chairman of J. I. Thornycroft and Co.
1907 The vehicle company completed its move into internal combustion engine power.
1913-1917 For a list of the models and prices of Marine Motors see the 1917 Red Book
1913-1917 For a list of the models and prices of Petrol Motor Commercial Vehicles see the 1917 Red Book
1914 Engineers, shipbuilders and motor manufacturers. Specialities: marine and mechanical engineering; torpedo craft and launches for river or sea service, propelled by either steam or oil engines; motor boats, motors, motor cars and wagons for heavy transport. Employees 4,000 to 5,000. 
Post-WWI: Awarded £4000 by the Royal Commission on Awards to Inventors for the depth charges and bomb throwers
1926 Received an order for twenty-three of their 'A1' type six-wheeled vehicles and a 'Hathi' tractor for use in the Sudan. Eighteen of the vehicles are to be fitted with platform bodies and to have two-wheeled trailer attachments to carry 20-cwt loads. The 'Hathi' tractor is to be capable of crossing gullies with vertical banks 3ft. in height, of exerting a steady draw-bar pull of 9000lb. of hauling a 10-ton trailer load up a gradient of 1 in 10 at 7 miles per hour, and of travelling through soft sand.
1948 The vehicle making side of the company was put into a wholly-owned subsidiary Transport Equipment (Thornycroft) to prevent confusion with the shipbuilding Thornycroft company.
1961 Works at Woolston Works, Southampton. Parent of eight subsidiaries. Employ 7,000 persons. The yard focused on making passenger/car ferries during the 60s along with tugs, motor launches and ferries. The Woolston yard then entered a period of modernisation with new equipment and buildings being built.
1961 Ship and boat building, ship and boat repairs, marine and industrial engineering. Shipbuilding includes: destroyers, frigates, minesweepers and all types of special service craft, also passenger and merchant vessels to 6,500 gross tons, tugs, ferries, shallow draft craft, motor and auxiliary yachts, fast and medium speed commercial and pleasure launches of wood, steel and glass fibre construction. 7,000 employees. 
1972 the new company purchased the Southampton repair yard of Harland and Wolff and continued making destroyers.
1977 The Woolston yard was nationalised in July 1977 and started making glass-reinforced plastic mine-hunters of the "Brecon" class.
1980s The yard continued winning orders for mine-hunters (for Saudi Arabia) and fast strike craft for Oman. The Vosper-Thornycroft yards returned to private ownership in 1986.
1990s The Omani Government made a further order for two corvettes armed with Exocet missiles. The yard continues to supply military hardware today under the VT Group name.
Sources of Information
- The Stock Exchange Year Book 1908
- 1914 Whitakers Red Book
- The Times, Jan 13, 1925
- The Engineer 1926/07/16
- The Engineer 1926/08/06
- 1961 Dun and Bradstreet KBE
- British Lorries 1900-1992 by S. W. Stevens-Stratten. Pub. Ian Allen Publishing
-  Wikipedia
-  Wikipedia
- Buses and Trolleybuses before 1919 by David Kaye. Published 1972
- The Engineer of 22nd October 1920 p400
- The Engineer of 13th July 1900 p31
-  Wikipedia
- British Shipbuilding Yards. 3 vols by Norman L. Middlemiss
- The Engineer of 23rd February 1894 p162
- The Engineer of 31st August 1894 p191
- The Engineer of 28th December 1894 p568
- The Engineer of 2nd April 1920 p345
- 1924 Naval Annual Advert page xix
- The Modern Diesel edited by Geoffrey Smith. Published by Iliffe & Sons 1944
- 1891 Post Office London Trades Directory
- Ian Allan - British Buses Since 1900 - Aldridge and Morris
- Biography of John Isaac Thornycroft by Alan G. Jamieson, ODNB