A father whose daughter was killed in the Paddington rail disaster has succeeded in getting the signal at the heart of the tragedy made safe.
Denman Groves' daughter Juliet, 25, was one of 31 people who died when her train hit an oncoming commuter service.
The safety measure means if a driver goes through a red light when another train is coming, a set of points on the track will automatically divert it.
Mr Groves said if the system had been in place in 1999 Juliet would be alive.
"It won't bring Juliet back but we just wanted it never to happen again and for it to be safe," he said.
Signal 109 was recommissioned in February this year after a major safety overhaul.
"Now all the things I've been shouting about over the last six years have been resolved. It shows what can be achieved by bereaved people.
"We've kept on badgering so people would know what had happened at Ladbroke Grove."
The disaster happened on 5 October 1999 when the 0603 GMT Cheltenham to Paddington train was hit head-on after the driver of a Thames Trains commuter service went through a red light.
Afterwards, a public inquiry headed by Lord Cullen produced three reports and 295 recommendations.
One was that the sophisticated Automatic Train Protection system to stop trains going through red signals must be in place on high-speed lines by 2008.
Lord Cullen also insisted that two independent bodies should be set up - one to investigate accidents and one to provide safety leadership across the industry.
In 2004, Thames Trains was fined a record £2m by an Old Bailey judge.
In his letter to Mr Denman, Network Rail chief executive Mr Armitt wrote: "Much has changed to the signalling system both in and around the Paddington area since the Ladbroke Grove tragedy.
"Signal SN109 and its approaches have been extensively modified.
"As you would expect, Network Rail continues to take its safety responsibilities extremely seriously."
Mr Groves has said he will continue to fight for and assurance the current speed restriction in and out of Paddington will not be lifted until the new measures come into use.