London has'd* many markets, but not so many market towns.
* a new word, which means "usually has, but currently doesn't".
To be a market town required a royal charter, back in the days when kings and queens granted retail favours. Each charter confirmed certain days of the week on which the market could open, and forbade other markets within 6⅔ miles from opening on the same day. Even in medieval times, royalty was adept at balancing economic competition with practical travelling times.
These market rights have now since passed to the local authority, but several places in London retain the historic right to call themselves market towns. They form an approximate ring around Westminster (whose market was granted its royal charter in 1256 but no longer trades). Some of the apparent gaps are plugged by market towns outside the existing boundaries of Greater London, for example Watford and Epping. [Full gazetteer]
Barnet:granted by King John, 23 Aug 1199(Thursday)
Barnet's original charter was granted to the Abbot of St Albans, and probably started off as a livestock market. It was originally located where Wood Street divides from the High Street. By the 14th century the area became known as Chipping Barnet, 'ceapen' being the Old English word for 'market'. Queen Elizabeth I granted a new charter in 1588, with market day changing to Mondays. Many of London's butchers came to Barnet at the start of the week to purchase cattle, which were kept on farms nearby and driven into town as needed. The market has moved numerous times (full history here). Fifty stalls currently trade round the back of The Spires on Wednesdays and Saturdays in the bandstand area beside Waitrose.
Enfield:granted by King Edward I, 8 Apr 1303(Monday)
Although Humphrey de Bohun and his heirs were granted a charter early in the 14th century, it took until the 15th for Enfield's market to become well established. The site has always been close to St Andrew's church. Sales stepped up in the 17th century when the present market place was created (21 stalls and 90 trestles were known to be trading in 1648). A market cross was added, which is now to be found in the rose garden at Myddelton House, and market day was switched to Saturday. The Enfield Society has an impressively full history here. Thursday trading started in 1974 and Fridays were added in 1987. The market's Instagram feed showcases the current (successful) set-up.
Romford:granted by King Henry III, 22 Sept 1247(Wednesday)
This one started out as a sheep market. Indeed it's sheep which originally defined the separation between different markets, six-and-two-thirds miles being the official distance sheep could be driven in one day. Romford's ducking stool survived beside the market place until the early 19th century. Today Romford boasts one of the largest street markets in the South East with over 100 regular stalls. A separate covered market (sorry, Shopping Hall) is semi-crammed with further nooks and eateries. Likely London's most genuine salt-of-the-earth market experience (Wednesdays, Fridays and Saturdays only).
Barking:granted by King Henry II, 1175-ish(day unknown)
The oldest of all Greater London's markets, because Barking was once a pre-eminent port and abbey town. Nobody's quite sure when precisely between 1175 and 1179 Henry II granted it a charter, only that its existence suddenly appears in the abbey's records. A market house was built in 1567 (since demolished, and its timbers incorporated into the doors of the 1950s town hall). The market's fortunes declined considerably as the town lost importance, and had ceased trading completely by the 1930s. Today it's back four days a week (Tuesday, Thursday, Friday, Saturday) along East Street, but very much for the cheap and convenient.
Woolwich:granted by King James I, 1618(day unknown)
This is the most recent market in the list, at a mere 400 years old, founded by royal charter in Stuart times. It started out by the ropeyard, then moved to Market Hill (in front of today's Waterfront Leisure Centre) before being shunted to what's still called Market Street. This proved too peripheral so traders moved back, then slowly took over the new square outside the Arsenal - a relocation officially recognised in 1879. The market's been in Beresford Square ever since, apart from a recent dalliance which nudged it briefly up Greens End, and I doubt any other London market has been given the runaround quite like this one. Come any day except Sunday, and don't set your sights too high.
Bromley:granted by King John, 19 Jul 1205(Tuesday)
The market was first held outside Bromley Manor, later moving to Market Square halfway down the High Street. A subsequent royal charter in 1447 switched market day to Thursday. In 1933 traffic improvements saw the market moved to the less convenient environs of the car park beside Bromley North station, returning to the High Street only in July 2012. The town remains inordinately proud of its royal origins, branding its assemblage of stallholders Bromley Charter Market to make the point. Every Thursday, Friday and Saturday it offers "an assortment of traditional, modern, speciality and staple goods, beautiful gifts, quality produce and delicious food", because this isn't Woolwich.
Croydon:granted by King Edward I, 10 Dec 1276(Wednesday)
Croydon's medieval marketplace occupied a large triangle of land now defined by the High Street, Surrey Street and Crown Hill. Corn was traded on one side and meat and livestock on the other, hence Surrey Street was originally called Butcher's Row. Over time this triangle was filled in by buildings, including a covered Butter Market, but all of this was comprehensively redeveloped by Croydon Corporation in the 1890s. This forced the market into Surrey Street where it remains today, trading every day except Sundays. A council refurb in 2017 means artisan produce and street food now intrude.
Kingston:granted by King John, 1208(day unknown)
Kingston has Saxon roots, and significant royal connections, but its first market charter appeared in the 13th century. Its location - the triangular Market Place - hasn't changed in centuries. A timber-framed town hall was built in the centre in Tudor times, with a ground floor open market supported on columns. The present Italianate building dates from 1840 and was renamed Market House in 1935. Kingston council gave the 'Ancient Market Place' a significant refurb in 2014, repaving the piazza with granite and introducing 29 permanent stalls in jagged wooden clusters. The emphasis is now more on cuisine and lingering with nibbles - a market for the ABC1s rather than the C2DEs.
Brentford:granted by King Edward I, 23 Dec 1306(Tuesday)
Brentford used to be a much more significant town, hence its medieval market charter. In 1550 an orchard behind the Crown Inn was taken over by traders (roughly where the Magistrates Court is now). The growing market passed through many owners in the 17th and 18th centuries, filling an area still known as Market Place today. To ease congestion a new Brentford Market was opened in 1893, on land to the east of Kew Bridge (now the Fountain Leisure Centre), specialising in fruit and veg from local market gardens. This closed in 1974, replaced by the Western International Market in Southall, and Brentford's current market is a Sundays-only shadow of its former self. Excellent histories here and here.
Uxbridge:granted by King Henry II, 1180(Thursday)
Uxbridge was a minor hamlet before the Lord of the manor of Colham, Gilbert Basset, was granted a market charter by the king in 1180. A prosperous market town grew up, and by 1513 a market-house had been built. At the turn of the 19th century Uxbridge boasted one of the largest corn markets in England, with a separate Saturday market for food and goods. The pillared Market House opposite the station dates back to 1788. In the 1970s Market Square was absorbed into the new Pavilions shopping centre, and trading (such as it is) now takes place in a dispiriting quadrangle between M&S and Iceland.
Other historic charter markets in the Greater London area: Lambeth (1199), Orpington (1206), West Ham (1253), Carshalton (1259), Harrow (1261), Rainham (1270), Plumstead (1270), St Mary Cray (1281), Eltham (1284), Chelsfield (1290), Hounslow (1296), Bexley (1315), Pinner (1336), Crayford (1396)