The scientists' plaques mark people who discovered how the world works. The inventors' plaques mark people who made a thing, and the difference is that you can usually point at the thing. Walk London with an eye for the blue discs and you pass the house of the man who solved longitude with a clock, the flat where the London A to Z was compiled by a woman who walked three thousand miles of streets, the address of the engineer whose tunnelling shield made the Underground possible, and a suburban home in Bromley belonging to Thomas Crapper. Very little of what fills an ordinary British day was invented far from this city.
This is a guide to the blue plaques of London's inventors and engineers, part of the wider blue plaque scheme that records the city's history house by house. It sits alongside our guides to the scientists, who mostly discovered rather than built, and the architects, who built at a rather larger scale.
Getting Around
At Summit House, Red Lion Square, a plaque records John Harrison (1693-1776), inventor of the marine chronometer, who lived and died in a house on the site. Harrison, a self-taught Lincolnshire carpenter, spent four decades solving the longitude problem, which had wrecked fleets and defeated the best mathematicians in Europe, by taking the unfashionable view that the answer was a clock accurate enough to keep time at sea. He was right, and he had to fight for years to be paid.
At 17 Sydenham Hill, a plaque marks Sir Francis Pettit Smith (1808-1874), pioneer of the screw propeller, the innovation that replaced the paddle wheel and made ocean-going steamships practical. At The Royal Victoria and Bull Hotel in Dartford, a plaque records Richard Trevithick (1771-1833), the Cornish engineer who built the world's first working steam locomotive and who died, largely forgotten and without money, in the hotel the plaque is on.
The railways have two more. At King's Cross station, a plaque records Sir Nigel Gresley (1876-1941), locomotive engineer, whose Mallard still holds the world speed record for a steam locomotive set in 1938. And at 3 St Mary's Grove in Barnes, a plaque marks James Henry Greathead (1844-1896), the tunnelling engineer whose refinement of the tunnelling shield made deep-level tube lines possible, which is the single reason the London Underground looks the way it does.
Two-wheeled and four-wheeled travel are here too. At Church Hill, Walthamstow, a plaque records John Kemp Starley (1855-1901), widely considered the inventor of the modern bicycle: his Rover safety bicycle of 1885, with two equal wheels and a chain drive, is essentially the machine still being sold today. At 14-15 Conduit Street in Mayfair, a plaque marks Charles Rolls (1877-1910), pioneer of motoring and aviation, who worked there in the years he was building the company with Henry Royce. And at 8 Philip Walk in Peckham, one records Edward Turner (1901-1973), designer of the Triumph Speed Twin, the engine layout that defined British motorcycling for forty years.
Communication
At 141 Cleveland Street, a plaque records Samuel Morse (1791-1872), described as an American painter and inventor of the Morse Code, who lived in London as an art student long before the telegraph. At 19 Park Crescent, a plaque marks Sir Charles Wheatstone (1802-1875), scientist and inventor, who with William Cooke patented the first commercially successful electric telegraph in Britain, and who also invented the concertina and gave his name to the Wheatstone bridge.
At 71 Hereford Road in Bayswater, a plaque records Guglielmo Marconi (1874-1937), the pioneer of wireless communications, who lived there in 1896 and 1897, the period when he arrived in London as a young man with a box of apparatus nobody in Italy had been interested in and set about demonstrating radio to the Post Office. At 94 Great Portland Street, a plaque marks David Edward Hughes (1831-1900), scientist and inventor of the microphone, and at 20 Outram Road, Addiscombe, one records Frederick George Creed (1871-1957), inventor of the teleprinter.
Two plaques mark the technologies that carried the twentieth century's sound and pictures. At 37 The Ridings in Ealing, a plaque records Alan Blumlein (1903-1942), the electronics engineer who invented stereo sound, patented it in 1931 with an insight so far ahead of the market that it went largely unused for twenty years, and who was killed testing airborne radar at 38. At 136 Maida Vale, a plaque marks William Friese-Greene (1855-1921), pioneer of cinematography, and at 287 Sheen Lane one records Sir Robert Watson-Watt (1892-1973), pioneer of radar, the system that gave Fighter Command the warning it needed in 1940.
At 79 Queen's Gate, a plaque marks Dennis Gabor (1900-1979), physicist and inventor of holography, who won the Nobel Prize for it, and at 32 Donne Place in Chelsea, one records Sir Clive Sinclair, inventor, who lived there from 1982 to 1987, the years of the ZX Spectrum and the C5.
The Everyday Things
The most enjoyable plaques in this collection mark objects nobody thinks about.
At 3 Court Lane Gardens in Dulwich, a plaque records Phyllis Pearsall (1906-1996), inventor of the London A to Z. The story she told was that she got lost using an out-of-date map in 1935 and resolved to make a better one, walking the city's 23,000 streets herself, some 3,000 miles, rising at five each morning and indexing entries on cards in shoeboxes. Historians have questioned parts of the account, and her father had been a mapmaker, but the atlas was real, the company was hers, and she ran it for sixty years.
At 12 Thornsett Road in Penge, a plaque records Thomas Crapper (1837-1910), engineer, described as the developer of the controlled flow cistern. He did not invent the flush toilet, which predates him considerably, and the vulgar word does not derive from him either, but he was a genuine sanitary engineer who held several patents, popularised the ballcock, and ran a successful firm, so the plaque is fairer than the folklore.
At 5 Denmark Street, a plaque marks Augustus Siebe (1788-1872), pioneer of the diving helmet, whose closed dress of 1837 was the basis of standard diving equipment for well over a century. At Banstead Court, Green Lanes, a plaque records Thomas Hancock (1786-1865), inventor and founder of the British rubber industry, who developed the masticator that made rubber workable and patented vulcanisation in Britain. And at 15 Northampton Square, Islington, a plaque marks Sir Henry Bessemer (1813-1898), whose converter made cheap steel possible and changed what could be built out of what.
At 118 Hillfield Avenue in Crouch End, a plaque records Carswell Prentice, described as the inventor of the supermarket trolley, which is a claim it is worth knowing London makes.
Two plaques mark inventions of systems rather than objects. At Burton Crescent, later Cartwright Gardens, a plaque records Sir Rowland Hill (1795-1879), pioneer of the modern postal service, whose 1840 reform replaced a chaotic distance-based system paid for by the recipient with a flat penny rate paid by the sender, and produced the postage stamp. And at 15 Wildwood Road, a plaque marks Frank Pick (1878-1941), pioneer of good design for London Transport, who commissioned the roundel, the Johnston typeface, and Harry Beck's diagram, and in doing so invented the idea that a public transport system should look like one thing.
Infrastructure and the Big Objects
At Cunard Crescent in Bush Hill, a plaque records Sir Hugh Myddelton, engineer of the New River, the artificial waterway completed in 1613 that brought clean water nearly forty miles into London and supplied the city for three centuries.
At 3 Kensington Gate, a plaque marks Sir Benjamin Baker (1840-1907), civil engineer and designer of the Forth Bridge, and at 145 Carlton Road, one records William Henry Barlow (1812-1902), engineer of the train shed at St Pancras, which was the largest single-span roof in the world when it opened. At 28 Willifield Way, a plaque marks Sir Ove Arup (1895-1988), the engineer whose firm made structures like the Sydney Opera House buildable.
At 57d Hatton Garden and again in Bexley, plaques record Sir Hiram Maxim (1840-1916), the American-born inventor who designed and manufactured the Maxim gun, the first true machine gun, in a workshop off Hatton Garden. It is one of the more sobering plaques in London: an invention that changed warfare more than almost any other, developed in a small building in a jewellery district.
At 55 Sheen Road in Richmond, a plaque records Ardaseer Cursetjee Wadia (1808-1877), the Parsi shipbuilder and civil engineer from Bombay who introduced steam navigation and gas lighting to India, and who in 1841 became the first Indian elected a Fellow of the Royal Society.
Why London
Invention needs three things that rarely occur together: somebody with a workshop, somebody with money, and somebody who wants the thing. London had all three within a few miles for two centuries. The instrument-makers and precision trades clustered around Clerkenwell and Hatton Garden, the patent agents and the Royal Society were in the centre, the docks and the railways created enormous demand for engineering, and the investors were in the City.
The pattern in the plaques reflects that. The heavy engineers are marked in comfortable Kensington and Richmond houses, because bridges paid well. The tinkerers are scattered through the suburbs, in Penge and Crouch End and Walthamstow, working in back rooms and small workshops. And a striking number of the plaques mark people who were not from here, Marconi, Morse, Maxim, Wadia, Gabor, Arup, because London was where you came to get an invention taken seriously.
An Inventors' London Walk
There is no tidy cluster, which suits picking a theme. For transport, start at Greathead in Barnes and Gresley at King's Cross and finish at Starley in Walthamstow. For communication, Marconi in Bayswater, Wheatstone on Park Crescent, and Hughes on Great Portland Street are all within a walk of each other, near the plaques in our guide to Marylebone.
For the most enjoyable trip, take the everyday things: Pearsall's A to Z in Dulwich, Crapper in Penge, and the supermarket trolley in Crouch End, three plaques for objects you will use again this week. If you want to find these plaques as you walk, and keep a record of the ones you have visited, Legacy maps every blue plaque in London, turning a day of exploring into a collection you build over time. The inventors' plaques are the ones that most reliably change how a walk feels, because after them the city stops looking like a backdrop and starts looking like a workshop.