On 4th February 1871 the Central Telegraph Office opened for the first time, today, it’s remembered among these iconic telecommunications buildings. 

Discover more about the UK's most important communications sites.

[Read more: Secrets of the BT Tower - what happened on the 14th floor]

The Central Telegraph Office, London

Central Telegraph Office

The Central Telegraph Office on Newgate Street and St Martin’s Le Grand in London dates back to the 1860s and was the initial home of the London-Paris telephone service from 1891-1904. In 1986 it played host to the first demonstration of wireless telegraphy.

However, the five-storey building, also in the shadow of St Paul’s Cathedral, was an obvious target during wartime due to its importance as a communications hub. It was hit during World War I, resulting in the death of a solider, before a Luftwaffe raid destroyed it in December 1940.

The building was eventually rebuilt in 1943. After the war it was the largest telegraph office in the world, with a direct line to every large town in the UK, but emergence of the telephone meant it never quite recovered its pre-war prominence.

It was demolished for safety reasons in 1967, but the BT Centre, which opened in 1984, now sits on the same site.

[Read  more: 'Mr Watson, come here I want to see you'  - the early days of the telephone]

Faraday Building, London

Faraday Building - BT

The home of the General Post Office’s first telephone exchange in 1902, the building - near St Paul's Cathedral in the City of London - remained of paramount importance until the 1980s. In 1904 a long-distance exchange was opened and by 1905 the site had exhausted its capacity of 10,000 phone subscribers, so a second exchange was built.

In the 1930s it played host to the first international telephone exchange and was dubbed ‘the switchboard to the world’. In November 1942, at the north east of the property the ‘Citadel’ secure telephone exchange was constructed. Built to withstand a direct hit from a medium-sized bomb, it had 6-foot-thick walls, a 7-foot-thick ceiling and no windows.

It meant that the GPO would be able to maintain services if the north and south buildings at Faraday were destroyed. It included dorms, a well, fuel storage tanks and power generators.

After enduring for decades after World War II (primarily because it was too difficult to demolish) it was removed to make way for a hotel in 2005.

[Read more: 9 telecoms technologies that changed our lives]

Electric Telegraph Company, Central Station, London

Electric Telegraph Company - Central Station

The Central Station of the Electric Telegraph Company in Lothbury was opened in January 1848 and was a predecessor of the CTO.

It sits in Founders Court behind the Bank of England and the exterior of the building remains largely the same to this day.

It was the beginning of the telegraph industry expanding beyond the railways to serve business and financial institutions. Footprints of London has a great page on the history of the building

The BT Tower, London

Arguably the most recognisable telecommunications landmark in the United Kingdom, the BT Tower towers over the central London skyline. Originally known as the Post Office Tower, it opened in 1965 and was initially capable of handling 150,000 simultaneous calls and transmitting 40 TV channels.

At 580-foot high (627 foot with the antennas) it was once the tallest building in the UK (but is now only the 11th tallest in London) and even had a rotating restaurant, which remained open until 1980. The public viewing gallery was closed in 1971 after a bomb exploded on the 33rd floor. Luckily no-one was hurt.

Check out the video below to find out more about the BT Tower.

Goonhilly Satellite Earth Station, Cornwall

Arthur

For 55 years the Goonhilly Earth Station assisted with terrestrial and extra terrestrial communications, including the moon landings.

Located on Goonhilly Downs in Cornwall, ‘Arthur’ was built in 1962 to track Telstar, the first active communications satellite. It delivered the first transatlantic pictures to the UK. That included the Apollo 8 moon orbit and the Apollo 11 lunar landing. After a spell as a visitor centre run by BT, it is now owned by Goonhilly Earth Station Ltd, which has doubled the amount of active satellite antennas on site.

[Read more: How Arthur brought the moon landings to British homes]

Broadcasting House, London

Broadcasting House

The global headquarters of the British Broadcasting Corporation was opened in 1932 and began transmitting radio broadcasts the same year.

The iconic spot in Portland Place, Westminster now provides live programming to 10 million people in the UK per week. A £1 billion extension opened in 2011 and now houses the newsrooms and studios.

Crystal Palace Transmitting Station, South London

Crystal Palace transmitter

The main television transmitter for the London area is 719ft tall, making it the fifth tallest building in the capital.

Designed and built for the BBC in 1951, it sits on the site of the old Crystal Palace, which was destroyed by a fire in 1936. Interestingly the first colour television broadcast tests were transmitted from the tower in 1956.

[Read more: 11 times celebrities tried tech]

Valentia Island, Ireland

Valentia Island

Valentia Island in West Ireland was the launch point for the first transatlantic cable, which carried all the way to Heart’s Content in Newfoundland, Canada.

The cable enabled Morse code transmissions across the Atlantic for the first time, but required a copper cable 20 times longer than had ever been built, laid at depths far beneath those linking Britain to Ireland and Europe. In 1857 the New York Herald described the endeavour as “the grandest work which has ever been attempted by the genius and enterprise of man”.

The site is currently bidding to become a UNESCO World Heritage Site.

Kingsway Telephone Exchange, London

Kingsway Telephone exchange

A network of tunnels below High Holborn in London, initially designed as a World War II air raid shelter, were handed over to the General Post Office when the war ended.

In 1956 it became the UK termination point for TAT-1, the first transatlantic telephone cable, and at the height of Cold War paranoia the Kingsway Exchange became a crucial resource - it was designed to withstand a nuclear blast and acted as the location for a Cold War hotline to enable communication between the Presidents of the US and Russia (via Abandoned Spaces).

The licensed staff bar, built 60 feet below street level, was the deepest in the UK and served up to 200 GPO employees.

Post Office Research Station, North London

Dollis Hill

The Dollis Hill site, now home to apartments, is where Colossus – the world’s first programmable electronic digital computer - was built in 1943. It was followed by nine Mark 2 models, which were used for the cryptanalysis of the Lorenz cipher at Bletchley Park during World War II.

Dollis Hill was a predecessor to the current Adastral Park site in Suffolk, which is occupied by BT Labs and other privately-owned enterprises.

[Read more: From the first phone call to the speaking clock - how the UK got connected]