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020

020 is the national dialling code for London in the United Kingdom.^[1] It covers the City of London, all 32 London boroughs, and parts of surrounding areas outside Greater London.^[2] Telephone numbers in this area consist of the code 020 followed by an eight-digit subscriber number.^[3]

History

Origins in the London Telephone Area

The telephone service in London originated in 1879, when the Telephone Company Ltd (Bell's Patents) opened Britain's first public telephone exchange at 36 Coleman Street, initially serving 8 subscribers through manual switchboards operated by human operators.^[4] That same year, the General Post Office (GPO) commenced its telephone business by providing rental telephones, primarily in Manchester, but soon expanded involvement in the network as private companies proliferated exchanges across the capital.^[4] These early manual exchanges relied on operators to connect calls via plug-and-cord switchboards, marking the foundational infrastructure for London's telephony before widespread automation.^[5] By the early 20th century, the GPO had consolidated control, acquiring the National Telephone Company in 1912 and managing a unified system with over 1,500 exchanges nationwide, including London's growing network of manual and emerging automatic facilities.^[4] Prior to the introduction of subscriber trunk dialling (STD), which began nationally in 1958, London's system operated without a dedicated area code, using local alphanumeric exchange names for routing calls within the city.^[4] This alphanumeric format, implemented in the 1920s with the Director system for larger urban areas like London, assigned memorable three-letter prefixes to exchanges—such as "ABB" for Abbey or "NAT" for National—followed by four digits, as in the example "ABBey 1234" used for London Transport inquiries from 1938.^[4]^[6] The shift toward modern dialling accelerated in the late 1950s as STD preparations required standardized numeric codes. On 6 April 1959, the GPO introduced the single "01" prefix for the entire London area, encompassing both inner and outer zones, to facilitate automatic national dialling and replace the alphanumeric system.^[4] This "01" code laid the groundwork for all-numeric numbering, with full implementation of numeric dialling across London exchanges occurring progressively through the 1960s, enabling direct subscriber access without operator intervention for local and trunk calls.^[4]

Development of STD Codes

The "01" code for the London telephone area, established in the 1960s as part of the UK's transition to all-figure dialling to support Subscriber Trunk Dialling (STD), remained in use throughout the 1970s and into the 1980s, covering the entire region with 7-digit local subscriber numbers. By 1979, when national STD coverage was fully completed, this system enabled direct dialing for trunk calls across the UK, with London's unified code handling the area's growing demand without initial splits.^[7]^[8] Rapid expansion in telephone usage during the late 1980s led to number exhaustion under the single "01" code, prompting a major restructuring on 6 May 1990. The code was divided into "071" for inner (central) London, encompassing core districts like Westminster and the City of London, and "081" for outer (suburban) London, including areas such as Ealing and Bromley. This split effectively doubled the available capacity by reallocating exchange codes, addressing the strain from London's dense population and business activity while preserving 7-digit local formats.^[9]^[10] Further adjustments came with the national PhONEday changes on 16 April 1995, which inserted a '1' after the initial '0' in area codes to standardize the UK's numbering plan and create room for long-term growth. Consequently, inner London's "071" became "0171" and outer London's "081" became "0181", maintaining compatibility with existing infrastructure and 7-digit local numbers. These modifications ensured sustained scalability amid ongoing telecommunications demands.^[11]^[10] Under the 0171 and 0181 systems, specific exchange codes distinguished localities; for instance, inner London numbers followed the format 0171 xxx xxxx (e.g., 0171 222 1234 for exchanges in central areas like Holborn), while outer London used 0181 xxx xxxx (e.g., 0181 333 4567 for suburban exchanges in places like Kingston). This structured allocation optimized resource use and supported efficient routing within the evolving STD framework.^[12]

The Big Number Change

The Big Number Change was a major national renumbering initiative in the United Kingdom, announced in the late 1990s to address the growing demand for telephone numbers driven by the expansion of mobile phones, internet services, and multiple household lines, which had strained the existing system.^[13] For London specifically, the change aimed to conserve numbers, simplify dialling, and unify the split inner (0171) and outer (0181) area codes under a single code, 020, thereby increasing overall capacity and accommodating future growth.^[13] This unification reversed the 1990 separation of London's codes and was part of a broader effort to create approximately 9 billion new numbers nationwide.^[13] The rollout for London occurred in phases to minimize disruption. New 020 numbers with eight-digit local formats were introduced on 1 June 1999, initiating a dual-running period where both old (0171/0181 + seven digits) and new (020 + eight digits) formats were accepted.^[14] This parallel operation lasted until 22 April 2000, when the old codes were fully decommissioned, and only the 020 format remained valid.^[14] A £20 million public awareness campaign, including advertisements and a dedicated helpline, supported the transition to inform users of the changes.^[13] Technically, the change involved adding a seventh and eighth digit to local numbers, transforming seven-digit subscriber numbers into eight-digit ones under the new 020 code.^[15] This adjustment increased London's telephone number capacity from 20 million to approximately 100 million possible combinations, creating space for an additional 80 million numbers to meet long-term demand.^[15] The dual-running period ensured continuity, with automated announcements redirecting calls to old formats during the overlap, preventing widespread service interruptions.^[13]

Coverage

Geographic Scope

The 020 area code serves as the national dialling code for the London telephone area, primarily covering all 32 London boroughs along with the City of London. This encompasses an area of approximately 1,572 km² and a population of approximately 9.1 million residents as of mid-2024.^[16] The coverage follows a roughly radial pattern, extending approximately 20 km from Charing Cross as the central reference point, and includes select parts of adjacent counties such as Hertfordshire, Essex, Surrey, and Kent.^[17] This configuration aligns closely but not identically with Greater London's administrative boundaries, incorporating some outer localities while excluding others based on telephony infrastructure. Regulatorily, the area is defined by Ofcom as a distinct geographic numbering zone under the National Telephone Numbering Plan, separate from postal codes or local government divisions to facilitate efficient allocation of subscriber numbers.^[1]^[18] Historically, the London telephone area evolved from the original zone established by the General Post Office (GPO) in the early 20th century, with key expansions and automation advancements occurring in 1922 when the GPO adopted the Strowger automatic exchange system to manage growing demand across the defined metropolitan region.^[19]^[4]

Specific Localities and Exceptions

The 020 area code covers the entirety of Greater London, encompassing all 32 London boroughs as well as the City of London. This includes all inner London boroughs, such as Westminster and Camden, and all outer London boroughs, such as Barnet and Bromley, with no exclusions within these administrative boundaries.^[20]^[21] Beyond Greater London, the code extends to select fringe areas in adjacent counties, including Bushey Heath in Hertfordshire, Chigwell in Essex, and Ewell in Surrey. Additional included localities comprise parts of Enfield (such as Crews Hill) and Hillingdon, along with other nearby communities like Borehamwood and Loughton, as well as Cuffley, Radlett, Molesey, Crayford, Erith, and Swanley. These extensions reflect historical telephone exchange allocations that link certain peripheral areas to the London numbering plan.^[20] Notable exclusions exist in outer suburbs adjacent to the 020 zone; for instance, Watford in Hertfordshire operates under the separate 01923 code. Croydon, including its fringes, remains fully integrated within the 020 area as an outer London borough, with no distinct exclusions.^[21]^[22] Exceptions to geographic tying apply to non-location-specific numbers, such as mobile services (typically starting with 07) and non-geographic numbers (such as those beginning with 03), which are not assigned based on the 020 locality and can be used nationwide regardless of the user's physical location.^[1]

Numbering and Allocation

Dialling Formats

The 020 area code follows the standard UK geographic numbering format, consisting of the three-digit area code followed by an eight-digit subscriber number (formatted as 020 X xxx xxxx, where X is a single digit such as 3, 4, 7, or 8), for a total of 11 digits when dialing nationally (e.g., 020 7123 4567).^[23] Within the London area covered by 020, local dialing from landline phones uses only the eight-digit subscriber number, excluding the area code, as defined in the National Telephone Numbering Plan where the "Local Number" is the geographic number without the area code.^[24] The numbering structure employs overlays, formatted as 020 X xxx xxxx, where X is a single digit (e.g., 3, 4, 7, or 8) and xxx xxxx comprises seven digits; this provides a capacity of $10^7 = 10 million numbers per overlay.^[25] Overlays 3 (introduced 2005), 7 and 8 (from 2000), and 4 (released late 2019) are in use, yielding a total allocated capacity of 40 million numbers across these four overlays.^[25]^[26] Internationally, 020 numbers are dialed in the E.164 format as +44 20 xxxx xxxx, replacing the leading 0 with the UK country code +44.^[27]

Code Overlays and Expansions

The 020 area code for London was established through overlays during the Big Number Change on 22 April 2000, when the previous inner London code 0171 was migrated to 020 7 xxx xxxx and the outer London code 0181 to 020 8 xxx xxxx.^[10] This transition unified the city's numbering under a single area code while retaining the third digit to distinguish inner (7) from outer (8) zones, thereby increasing overall capacity from the prior split system without requiring changes to local dialing.^[10] To accommodate rising demand and prevent exhaustion in the established ranges, Ofcom introduced the 020 3 xxx xxxx overlay in early 2005 as an additional geographic numbering block for Greater London.^[28] This expansion added roughly 10 million numbers, functioning similarly to an overlay by covering the same geographic area and enabling seamless integration into the existing 020 framework.^[28] By 2019, the combined 020 3, 7, and 8 ranges faced imminent depletion, prompting Ofcom to release the 020 4 xxx xxxx range, which provides approximately 10 million new numbers primarily for geographic allocations in London. Applications for these numbers began on 1 October 2019, with customer allocations starting in December 2019, to sustain supply amid London's population and business growth.^[29] Following the near-exhaustion of the 0203 range around 2020, the 0204 range has become the primary source for new geographic assignments to manage ongoing demand. As of the latest available data (2022), Ofcom continues to monitor demand for London numbers, with potential for future overlays if needed.^[30]

Usage and Regulations

National and International Dialling

Within the United Kingdom, all calls to 020 numbers require dialing the full national format of 020 followed by the eight-digit subscriber number, regardless of the caller's location, including from within the London area itself. This uniform national dialing procedure was implemented during the Big Number Change on 22 April 2000, which phased out shorter local dialing codes previously used in London and mandated the complete 10-digit format to avoid conflicts with other number ranges, such as mobile numbers starting with 07.^[31]^[15] Internationally, 020 numbers are accessed by dialing the international exit code for the originating country (such as 00 in most of Europe or 011 in North America), followed by the United Kingdom's country code +44, then 20 (omitting the leading zero from the area code), and the eight-digit subscriber number, yielding the format +44 20 xxxx xxxx. In this context, 020 functions as a two-digit area code under the International Telecommunication Union standards incorporated into the UK's National Telephone Numbering Plan.^[32] Special dialing rules apply for emergencies, where 999 or the European equivalent 112 can be dialed directly from any UK-connected phone, overriding standard geographic routing to connect callers to police, ambulance, or fire services without needing the full 020 prefix. Since the early 2000s, following regulatory liberalization, 020 numbers have supported portability to Voice over Internet Protocol (VoIP) providers and mobile networks, enabling their use from any physical location without restrictions tied to the original London geographic association, as long as the service complies with Ofcom's numbering conditions.^[33]^[34] A common issue post-2000 was mis-dialing stemming from familiarity with the pre-change 0171 (inner London) and 0181 (outer London) codes, leading some callers to incorrectly treat 0207 and 0208 as distinct area codes rather than sub-ranges under 020; however, public awareness campaigns and the mandatory full-dialing enforcement resolved most such errors by the end of the dual-running period in late 2000.^[31]^[15]

Charging Groups and Costs

The 020 area code is classified as a geographic number under the UK's National Telephone Numbering Plan, charged at standard geographic rates for 01 and 02 prefixes, which are generally cheaper than calls to non-geographic numbers such as 08xx.^[35] These rates vary by distance from the caller but apply uniformly across the 020 area without distinctions based on specific locations within London. Following the Big Number Change in 2000, charging for 020 numbers was unified, eliminating the prior split between inner and outer London codes (previously 0171 and 0181), with all calls treated under a single geographic structure; historical charging groups for zonal pricing are no longer applicable.^[36] Ofcom has overseen this framework through the National Telephone Numbering Plan since 2006, ensuring consistent regulation of geographic numbering and billing. Local calls to 020 numbers are typically free or included in most landline and mobile bundles. In practice, as of 2025, calls to 01 and 02 numbers are often included in unlimited allowances on most landline and mobile tariffs, making them effectively free within those plans. For out-of-plan national calls from landlines, costs are up to 16p per minute depending on the provider, time of day, and any connection fees (up to 23p for some providers), as of 2023.^[37] From mobiles, rates range from 3p to 65p per minute, as of 2023, often bundled in plans.^[35] International calls to 020 numbers vary widely by provider and destination but follow standard international geographic tariffs. No premium rates apply under the 020 prefix, as it is reserved for geographic use.^[37] Overlays such as 0203 and 0204, introduced to expand capacity, maintain standard geographic billing and are frequently allocated for corporate lines.^[38]

References

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