BT will next month start an 8mbps broadband trial as it prepares to offer the much faster service to some companies and domestic users by the end of the year.
When the standard for ADSL broadband was finalised at the end of the 1990s, the potential 8mbps speed was set out.
However, when BT launched its first ADSL services in 2000 it decided to start with 500kbps as standard.
BT said the trials are in response to broadband applications such as video-over-broadband and broadband TV.
Speeds of 8mbps are dependant on the state of the copper wire on which the data travels.
Last month, BT upgraded the standard broadband speed of most business customers from 500kbps to 2mbps, at no extra charge.
The trial, involving BT employees, will last 10-12 weeks but tests will continue up until the commercial launch, the telco said.
BT rival Bulldog already provides 4mbps access to London customers.