While early plans to serve Wood Green (specifically Alexandra Palace) existed since the 1890s as part of the GN&SR, this short section to Finsbury Park was later dropped from the GNP&BR proposal in 1902 when the company was bought over.
In 1902, as part of an agreement for buying over the GN&SR, The Great Northern Railway (GNR) imposed a sanction on Yerkes to abandon the section north of Finsbury Park and they would construct the terminus below ground.
Finsbury Park remained as an overcrowded terminus of the line, and was described as "intolerable".
Many passengers had to change onto buses, trams, and suburban rail services to complete their journeys up north.
The GNR attempted to address this issue by considering electrification frequently, but to no avail due to shortage of funds.
Meanwhile, the LER proposed an extension in 1920 but was overruled by the GNR, which was widely regarded as "unreasonable".
In 1923, a petition by the Middlesex Federation of Ratepayers to repeal the 1902 parliamentary act emerged.
It was reported that "fierce exchange of arguments" occurred during a parliament session in March 1924 to request for this change.
Frank Pick, as the new Assistant Managing Director of the Underground, distributed photographs of the congestion at Finsbury Park to the press.
All of this pressure finally prompted the government to initiate "The North and North-East London Traffic Inquiry", with initial reports only recommending a one-station extension to Manor House.
The London and North Eastern Railway (LNER), being the successor of the GNR, was placed in the position of electrifying its own services or withdrawing its veto to an extension of the Piccadilly line.
With again insufficient funds to electrify the railway, the LNER reluctantly gave into the latter decision.
An extension was highly likely at this stage, based on a study in October 1925 by the London & Home Counties Traffic Advisory Committee.

Pick, together with the Underground board began working on the extension proposal.
Much pressure was also received from a few districts such as Tottenham and Harringay, but it was decided that the optimal route would be the midpoint of the GNR and the Hertford Line.
This was backed by the Committee, and parliamentary approval for the extension was obtained on 4 June 1930, under the London Electric Metropolitan District Central London and City and South London Railway Companies Act, 1930.
Funding was obtained from legislation under the Development (Loan Guarantees and Grants) Act instead of the Trade Facilities Act.
The extension would pass through Manor House, Wood Green and Southgate, ending at East Barnet (now Oakwood); based on the absence of property development along the line.
In November 1929, the projected terminus was later shifted further north to Cockfosters to accommodate a larger depot.
Ridership was estimated to be 36 million passengers a year on the extension, costing £4.4 million.
Stations were designated at Southgate, Arnos Grove, Bounds Green, Wood Green, Turnpike Lane, and Manor House, in addition to East Barnet.
St. Ann′s Road or Harringay Green Lanes was originally part of the scheme, but was dropped to maintain high average speeds in between stations.
This also compensated for a more expensive provision for construction of a third track between Finsbury Park and Wood Green.

Tunnel rings, cabling and concrete were produced in Northern England, while unemployed industrial workers there helped in the construction of the extension.
Construction of the extension started quickly, with the boring of the twin tube tunnels between Arnos Grove and Finsbury Park proceeding at the rate of a mile per month.
22 tunnelling shields were used for the tunnels, and tunnel diameters were slightly larger than the old section, at 12ft.
Sharp curves were also avoided to promote higher average speeds on the extension.
400 ft (120 m) long platforms were originally planned for each station to fit 8-car trains, but was cut short to 385 ft when built.
Some stations were also built with wider platform tunnels to cater to exp
While early plans to serve Wood Green (specifically Alexandra Palace) existed since the 1890s as part of the GN&SR, this short section to Finsbury Park was later dropped from the GNP&BR proposal in 1902 when the company was bought over. In 1902, as part of an agreement for buying over the GN&SR, The Great Northern Railway (GNR) imposed a sanction on Yerkes to abandon the section north of Finsbury Park and they would construct the terminus below ground. Finsbury Park remained as an overcrowded terminus of the line, and was described as "intolerable". Many passengers had to change onto buses, trams, and suburban rail services to complete their journeys up north. The GNR attempted to address this issue by considering electrification frequently, but to no avail due to shortage of funds. Meanwhile, the LER proposed an extension in 1920 but was overruled by the GNR, which was widely regarded as "unreasonable". In 1923, a petition by the Middlesex Federation of Ratepayers to repeal the 1902 parliamentary act emerged. It was reported that "fierce exchange of arguments" occurred during a parliament session in March 1924 to request for this change. Frank Pick, as the new Assistant Managing Director of the Underground, distributed photographs of the congestion at Finsbury Park to the press. All of this pressure finally prompted the government to initiate "The North and North-East London Traffic Inquiry", with initial reports only recommending a one-station extension to Manor House. The London and North Eastern Railway (LNER), being the successor of the GNR, was placed in the position of electrifying its own services or withdrawing its veto to an extension of the Piccadilly line. With again insufficient funds to electrify the railway, the LNER reluctantly gave into the latter decision. An extension was highly likely at this stage, based on a study in October 1925 by the London & Home Counties Traffic Advisory Committee.
Pick, together with the Underground board began working on the extension proposal. Much pressure was also received from a few districts such as Tottenham and Harringay, but it was decided that the optimal route would be the midpoint of the GNR and the Hertford Line. This was backed by the Committee, and parliamentary approval for the extension was obtained on 4 June 1930, under the London Electric Metropolitan District Central London and City and South London Railway Companies Act, 1930. Funding was obtained from legislation under the Development (Loan Guarantees and Grants) Act instead of the Trade Facilities Act. The extension would pass through Manor House, Wood Green and Southgate, ending at East Barnet (now Oakwood); based on the absence of property development along the line. In November 1929, the projected terminus was later shifted further north to Cockfosters to accommodate a larger depot. Ridership was estimated to be 36 million passengers a year on the extension, costing £4.4 million. Stations were designated at Southgate, Arnos Grove, Bounds Green, Wood Green, Turnpike Lane, and Manor House, in addition to East Barnet. St. Ann′s Road or Harringay Green Lanes was originally part of the scheme, but was dropped to maintain high average speeds in between stations. This also compensated for a more expensive provision for construction of a third track between Finsbury Park and Wood Green.
Tunnel rings, cabling and concrete were produced in Northern England, while unemployed industrial workers there helped in the construction of the extension. Construction of the extension started quickly, with the boring of the twin tube tunnels between Arnos Grove and Finsbury Park proceeding at the rate of a mile per month. 22 tunnelling shields were used for the tunnels, and tunnel diameters were slightly larger than the old section, at 12ft. Sharp curves were also avoided to promote higher average speeds on the extension. 400 ft (120 m) long platforms were originally planned for each station to fit 8-car trains, but was cut short to 385 ft when built. Some stations were also built with wider platform tunnels to cater to exp
Piccadilly line