The first stage of a project to build one of the world's most advanced telephone networks has been completed.
Laura Wess is first to make phone call on 21CN
The so-called 21st century network (21CN) is being built in the UK using Internet Protocol technology.
The massive upgrade, the first of its kind, will cost British Telecom £10bn and take until 2010 to complete.
It will open the way to new services as well as making existing services quicker and cheaper than before.
1,500 man years
The first person to use the new network was schoolgirl Laura Wess from South Wales.
The eleven-year-old spent a minute and a half chatting to the Right Reverend John Davies, the bishop of St Asaph.
She was chosen for the landmark call as she is one of the residents of Wick, near Cardiff, which is the first village to be upgraded to 21CN.
There is a lot of work to do in transforming the network
"Today marks a symbolic and momentous occasion for BT, the communications industry, for Wales and the rest of the UK as 21CN, over three years in the making, starts to become real for customers," said Paul Reynolds, chief executive of BT Wholesale.
BT has so far rebuilt around 10% of its network, laid more than 2,300 kilometres of new fibre optic cable in South Wales and invested more than 1,500 man years in developing the systems to support the new network.
Customers in Cardiff, Bridgend and Pontypridd will be the next to be transferred. The upgrade does not require customers to have a new telephone or number and can be done without an engineer visiting the premises.
Voice, data, broadband and multimedia services will all be carried on the new network. It will allow for faster broadband speeds as well as opening the door for services not yet thought of.