TAT1 was the first trans-Atlantic telephone cable, inaugurated on 25 September 1956. Designed to link both the US and Canada to the UK, it provided 30 telephone circuits to the US and 6 to Canada, as well as some telegraph circuits to Canada.

Extra circuits were designed with a leasing facility. There were then leased to other West European countries, giving them direct communication with US and Canada. The leased circuits were permanently connected through London to Germany, France, the Netherlands and Switzerland A circuit for was split between Denmark, Norway and Sweden.

On 1 December 1953 the UK Postmaster General announced that an agreement been signed. between the UK Post Office Engineering Department, the Long Lines Department of American Telegraph and Telephone Company, Bell Telephone Laboratories and the Canadian Overseas Telecommunications Corporation. 50% of the shares were held by the American companies, 40% by the Post Office and 9% by the Canadian Corporation.

The cable landing spots were sited in Newfoundland and Scotland, the most direct routes had already been taken by telegraph wiring. The Scottish site was a few miles south of Oban, and was linked by a coaxial cable line via Glasgow to International Exchange, London. On the American side the cables came ashore at Clarenville, Newfoundland, then crossed the Cabot Strait to Sydney Mines, Nova Scotia. This was connected to the US border via a line-of-sight microwave radio link to New Brunswick, Maine, where the route also branched to Montreal.

The cable was laid by the cableship 'Monarch'. The cable itself was amoured by steel, to protect against damage and was manufactured at Erith, Kent, with one way repeaters designed by Bell. The section of cable laid in the Cabot Strait used two way repeaters designed by the Post Office.

The project was completed 3 months ahead of schedule, taken a total of 3 years to complete, at a cost of £120 million.

The service was opened by the Postmaster General at 4.00 pm on 25 September 1956 in Lancaster House, London. He spoke to the Chairman of AT&T in New York, and to the Canadian Minister of Transport.

In the first 24 hours of public service there were 588 London to the United States calls and 119 from London to Canada.

Except for the peak period between 3.00 and 5.00 pm GMTcalls were connected within 10 minutes and the Post Office announced in 1957 "it is rare for any call to be delayed beyond an hour, except for causes outside the operator's control".

During its first year of service TAT 1 carried twice as many calls as the radio circuits had done in the year, around 220,000 calls between Britain and the United States, and 75,000 between Britain and Canada. This brought in £2 million revenue split between the three countries.

Summarised from information provided by the BT Archives and Historical Information Centre

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