BT was fined £300,000 today after a judge said a "significant failing" by the company contributed to the death of one its engineers.
David Askew, 52, died after falling from a stepladder while working at the Canonbury Telephone Exchange, north London, in October 2006.
The experienced engineer was standing on the top rung of the seven-foot ladder and working alone at the time of his death, Southwark Crown Court, central London, heard.
The accident resulted in BT being convicted of failing to ensure the health and safety of its employees at a trial in October this year.
Judge Deborah Taylor said the company had not provided appropriate ladders, leading Mr Askew to use a wooden ladder he found on the site.
Staff working at heights had also been given "erroneous advice" in BT's manuals, which did not consider the most up-to-date legislation, she continued.
She said: "This was a significant failing by BT, whose employees regularly work at height."
"In my judgment these failures by BT contributed to Mr Askew's fall," she concluded.
Judge Taylor noted that Mr Askew's widow, Denise, was in court for the sentencing and said: "I take into account the great personal loss to her and rest of the family. He clearly was an exceptional man."
She said the value of the fine "does not attempt to value the life of Mr Askew that was so tragically lost."
As well as the fine BT was also ordered to pay £196,000 costs.
Ronald Thwaites QC, mitigating, said that the odds of being killed by lighting were 10 million to one, while BT employees carried out nine million climbing jobs a year.
He said: "If, on a statistical basis, deaths from falls were only as likely as death by lightning bolt strikes, most people would recognise that is a fairly remarkable record."
In a statement, BT said it planned to appeal against the conviction.