Had history taken a slightly different twist, the modern tube map would look very different. You might be catching the Circle line from Devil's Acre to The Steelyard, or riding the DLR out to Chinatown.
All the places in the map once existed, and were well known. Most linger on in some form — perhaps as a street or local business name — but are no longer used as common terms for areas.
Adelphi: the term is Greek for 'brothers', a hint at the fraternal relationship of this area's developers: John, Robert, James and William Adam. Their Adelphi Terrace, between Strand and the Thames, was such a landmark, it gave its name to the local area. The term is occasionally used today, but has no common currency.
Agar Town: former name of the land around Agar Grove in King's Cross. The estate of low-quality housing lasted from 1841 to 1866, when the area's railways were built.
Alsatia: an area south of Fleet Street covering the site of the former Whitefriars monastery. Between the 15th and 17th centuries, it maintained a right of sanctuary, making it a safe haven for shadier types. The area was brought to life in Michael Moorcock's curious novel-cum-biography The Whispering Swarm.
Battersea Fields: old name for the land that became Battersea Park in 1858. It was a famous duelling ground, favoured by the Duke of Wellington.
Battle Bridge: in use until the 1840s when a short-lived monument to George IV forever changed the area to King's Cross. Battle Bridge is assumed to refer to an ancient bridge over the River Fleet, which still flows beneath the station. Connections to the battle between the Romans and Boudica are speculative at best. Battlebridge Basin on the Regent's Canal recalls this former name.
Bedlam: the Hospital of St Bethlehem, better known as Bedlam, has cared (or otherwise) for the mentally ill since the 13th century. It's existed in a number of locations, including the Imperial War Museum building and its present home in Beckenham. Its first two homes, however, were at the northern edge of the City. The hospital was so notorious — and a popular visitor attraction — that the wider area became synonymous with its presence.
Biscuit Town: nickname of the area around the former Peek Freans biscuit factory in Bermondsey, a company that gave us the bourbon biscuit, Twiglets and garibaldi biscuits.
The Brill: a supposed former Roman camp, the name was in use into the 19th century. It's remembered today in the name of two streets and a Cally Road restaurant.
Brook Field: an ancient name for part of Mayfair, where the Tyburn brook once babbled. Brook Street remembers the name.
Chinatown: long before its association with Leicester Square, London's Chinese population gravitated towards the area between Limehouse and Poplar. Chinatown was often portrayed, with grotesque exaggeration, as a den of iniquity, full of opium dens and vice. The area maintained its oriental connections well into the 20th century, slowly dispersing with the demise of the docks. Numerous road names recall the community, including Canton Street, Mandarin Street, Pekin Street, Ming Street and Nankin Street.
Clare Market: London School of Economics occupies the former neighbourhood of Clare Market, a rabbit warren of ancient houses, butchers' shops and — in its latter days — crushing poverty. The area was swept away by the Kingsway and Aldwych developments in the infant years of the 20th century. A pedestrian street of the same name still cuts through the area, and an ennobled head of LSE took the title Baron Dahrendorf of Clare Market in 1993.
Cripplegate: An ancient Roman entrance to the city, Cripplegate gave its name to the wider area around what is now Barbican station. Almost every building was destroyed during the Blitz, to be replaced by the concrete wonderland of the Barbican estate. The name is still in use as a City ward, and in the church of St Giles Cripplegate, but it can hardly claim a term in everyday use. The area also contained Grub Street, a district famous for its impoverished hack writers.
Crystal Palace: We now associate the name with part of Sydenham. The great glass funhouse originally stood in the southern part of Hyde Park, for one year only in 1851. This one's a bit of a cheat, as the glasshouse didn't remain long enough to bestow its name on the wider area, but it was such an impressive, dominant structure that we've included it anyway.
Devil's Acre: A notorious slum, centred on Old Pye Street, just a turd-hurl from Westminster Abbey. It was eradicated during the construction of Victoria Street in 1850. More here.
Five Fields: Ancient name for the blessed realm of Belgravia, before all those stucco houses and embassies took over.
Fleet Ditch: the story of the River Fleet is so well known, we're not going to go into any detail here. Suffice it to say, that the route of King's Cross Road, Farringdon Road and Farringdon Street was formerly the River Fleet, and would have been a major geographical feature in this part of town until covered over through the 18th and 19th centuries.
Grand Surrey Canal: south London once boasted its own canal, running from the Thames to Peckham. Much of it lasted right up to the 1970s, but most has now been filled in. Remnants can be found in Burgess Park, with a linear park following the route from there down to Peckham.
Hatcham: the original name for New Cross, dating back to Anglo-Saxon times. It survived until the mid-19th century, when the coming of the railways brought the change (the stations were built on New Cross Road). Several local organisations and businesses maintain the former name, and it can be seen here on the Liberal Club building.
Horsleydown: once a widely known area of Bermondsey, the place name Horsleydown has long fallen out of popular use. The former parish church is a curious beast. What looks like a modern brick building is, on closer examination, built on the base of the ecclesiastical building.
Lambeth Marsh: ye olde term for the low-lying ground around the Waterloo area. The term disappeared once the area was developed in the mid-19th century, but lingers on in Upper Marsh.
Lamb's Conduit Fields: the eastern parts of Bloomsbury remained largely undeveloped into the 19th century. These open fields, alongside Coram's Fields, were a noted cricket venue until the construction of the Foundling Hospital in 1739. Lamb's Conduit Street and Lacon House recall the former name.
The Mint: a place of coinage in the Tudor era, the area in Southwark retained the name of The Mint long after the facility closed. In subsequent centuries, The Mint had the status of a liberty, offering sanctuary to the criminal and persecuted.
The Mount: Whitechapel's most salient landmark is today the Royal London Hospital. In days of yore, a striking hillock was the most notable sight. Probably an ancient natural feature, the Whitechapel mount was used as part of the city-encircling Civil War defences. It was cleared away in the first half of the 19th century, but is remembered in nearby Mount Terrace.
Newington: this ancient name hasn't quite disappeared from the maps. Formerly a distinct settlement, the name is still remembered in Newington Butts, Causeway and Gardens, and is also the name of an electoral ward. However, the area is now almost always referred to as Elephant and Castle.
Old Nichol and The Jago: the Old Nichol, between Shoreditch High Street and Bethnal Green Road, was one of London's most notorious slum areas. A fictional account of the area was given in Arthur Morrison's 1896 novel A Child of the Jago, which popularised a second nickname for the area. The whole was swept away at the turn of the 20th century, with the creation of the Boundary Estate. Old Nichol Street still runs through the area, and a fashion shop called A Child of the Jago trades off Great Eastern Street.
Pedlars Acre: Old name for the acre (and a bit) beneath County Hall. Its name can be traced back to 1504, and has a rather cute story attached to it, as told on this website.
Placentia: Greenwich Park and its environs were once part of the Tudor palace of Placentia. Three monarchs were born here (Henry VIII, Mary I, Elizabeth I) and one died (Edward VI). The palace was demolished in 1660.
Ratcliff: once a common name for the community between Wapping and Limehouse, , the area fell into infamy after a series of gruesome murders in 1811. The name is rarely used today. Ratcliff Highway became simply The Highway.
Steelyard: beneath Cannon Street rail bridge, you'll find a plaque to the Steelyard. This riverside enclave served as a major trading centre for the Hanseatic League in the 15th and 16th centuries (though present in some form long before, and after). The name remains in Steelyard Passage (where you can still see an old Banksy rat), and the Steelyard night club.
St George's Fields: like Lambeth Marsh, the name was in common use until widely developed in the mid-19th century. The fields spread over an undefined area between the Elephant and the river, and are remembered in St George's Circus (below) and St George's Cathedral.
Stratford Marsh: old name for the river-riddled lands between Stratford and Hackney Wick. The term still has some currency, but looks like disappearing in favour of 'the Olympic Park'.
Surrey Commercial Docks: aerial photos or maps of the area before the 1960s reveal just how much of the Rotherhithe peninsula was once water (or associated warehousing). All but a handful of these once bustling docks were filled in during the 1980s and 1990s to make way for housing, though Surrey Quays Overground station retains part of the name.
Thorney Island: Westminster Abbey and the Houses of Parliament occupy land that was once an island, formed between two forks of the River Tyburn, where they met the Thames. The name is thought to reflect the once prickly nature of the undergrowth on the island. It has long been out of use, but is perpetuated in the Thorney Island Society, a local history and campaign group.
Tothill Fields: The northern end of Pimlico was once known as Tothill Fields. A famous gaol, the Tothill Fields Bridewell, stood here between 1618 and 1884, granting a wider notoriety to the area. The name disappeared as the once marshy land became developed.
Tyburnia: a 19th century name for the lands south of Paddington, and close to the River Tyburn and the Tyburn gallows. The name has recently seen a resurgence. Few Londoners can afford to live here, and there's little reason to visit unless you want to jeer at Tony Blair. Hence, the name remains obscure and forgotten.
Please suggest additions to the map in the comments below.
More information: Tom Bolton's 2014 book The Vanished City: London's Lost Neighbourhoods goes into good details about a handful of the areas in this article.
Updated 13 July 2016 to include Pedlars Acre.