[4] The site acts as a ground station for a number of satellites operated by the US National Reconnaissance Office,[5] on behalf of the NSA, with antennas contained in numerous distinctive white radomes, locally referred to as "the golf balls", and is alleged to be an element of the ECHELON system.

The other two sites are located in America and Australia, having similar roles and working together with RAF Menwith Hill to develop knowledge around American, British and Australian interests.

In 1954, the British War Office purchased 246 acres (100 hectares) of land at Nessfield Farm, located approximately 7 kilometres (4.3 mi) west of Harrogate, North Yorkshire.

However, if the site was compromised during an invasion, three earth-covered bunkers contained ammunition and thermite charges which could be used to destroy classified equipment and material.

[8] The station initially comprised a headquarters building, barracks, dependent housing and support facilities such as a cinema and social clubs.

[10] The operations building was located inside a secure compound, within a large antenna field, approximately 1.6 kilometres (0.99 mi) from the main site.

Therefore, on 1 August 1966, with the agreement of the British Government, control of Menwith Hill Station was handed from the US Army to the NSA when it became a field element of the agency.

[11] The first two radomes, designed to protect satellite receiver and transmission dishes (colloquially known as 'golf balls' and now synonymous with the station) were installed in 1974, at which point around 800 personnel were believed to work there.

Investigations found that during the early 1960s, Menwith Hill was integrated into the General Post Office's microwave relay network known as 'Backbone', via a high-capacity underground cable link to the Hunters Stones communications tower, located approximately 3 miles (4.8 km) to the south of the station.

It was alleged the link allowed mass interception of civilian telephone and telex communications between the United States, UK and Europe.

[18] On 19 July 2002, US Army INSCOM transferred responsibility for administrative and logistical support for Menwith Hill to the US Air Force, to bring the site in-line with other facilities in the UK made available to the US.

[22] In March 2012 researcher Steve Schofield of BASIC produced a 65-page report called "Lifting the Lid on Menwith Hill",[23] funded by the Joseph Rowntree Charitable Trust and commissioned and published by the Yorkshire Campaign for Nuclear Disarmament (CND).

The base's multimillion-pound expansion, Project Phoenix, is "one of the largest and most sophisticated high technology programs carried out anywhere in the UK over the last 10 years".

[24] During the 2009 G-20 London Summit NSA intercept specialists based at Menwith Hill attempted to target and decode the encrypted telephone calls of the Russian president Dmitry Medvedev.

Although designated as an RAF station, it is made available to the United States Department of Defense (DOD) under the 1951 NATO Status of Forces Agreement and other classified arrangements.

[35] On 1 April 2006, RAF Menwith Hill was designated as a protected site for the purposes of Section 128 of the Serious Organised Crime and Police Act 2005.

[36] In 1988, investigative journalist Duncan Campbell revealed, in an article entitled "Somebody's listening" and published in New Statesman, the existence of the ECHELON surveillance program, an extension of the UKUSA Agreement on global signals intelligence Sigint.

[37] Duncan Campbell presented a report commissioned by STOA concerning the ECHELON system, at a "hearing of the Committee on Citizens Freedoms and Rights, Justice and Home Affairs on the subject the European Union and data protection" which prompted the European Union to set up the Temporary Committee on the ECHELON Interception System.

[41] On 3 November 1999, the BBC reported that they had confirmation from the Australian Government of the existence of a powerful "global spying network" codenamed Echelon, that can eavesdrop on every single phone call, fax or e-mail, anywhere on the planet" with Britain and the United States as the chief protagonists.

[44] Objections to the Strategic Defense Initiative have led to demonstrators storming the perimeter fence,[45][46] and to demands in 2007 from Labour MPs for a full debate about missile defence and Menwith Hill.

[54] Protesters said they hoped the camp would "reignite the debate locally, nationally and globally about whether the subversive and undemocratic nature of activities at the base are acceptable, or indeed accountable, to the British public.