The second voice of the Speaking Clock, Pat Simmons, has died aged 85.
BT awarded Miss Simmons £500 when she won the clock competition
Miss Simmons, whose recorded voice announced the time on the BT service from 1963 until 1985, died at the Royal London Hospital in East London.
Her successor Brian Cobby described her as "a very sweet and charming woman" who would be "sorely missed".
BT chairman Sir Christopher Bland also expressed his condolences, saying: "Pat's voice was one of the most recognisable in Britain."
Sir Christopher said: "We were extremely saddened to hear that Pat Simmons had passed away, and our condolences go to her family and former colleagues at BT.
"She won an army of fans and was trusted by the millions of people who regularly called the speaking clock to find out the time."
Miss Simmons' solicitors said she had died on 29 October.
A childhood friend of Miss Simmons, Eileen White, told the Daily Telegraph Miss Simmons was "perfect because she had a beautiful voice".
"She became quite famous. But she used to laugh and laugh about the marriage proposals and fan mail."
The Speaking Clock was introduced in London in July 1936 and went nationwide in 1942.
Prior to its installation, customers had to ring the telephone operator to get "the time by the exchange clock".
The first voice on the Speaking Clock was that of Miss Jane Cain, a telephonist, who won a prize of 10 guineas (£10.50) in a competition to find the right voice.
The clocks which used her voice were replaced in 1963 and Miss Simmons - a supervisor in a London telephone exchange - won a £500 competition to replace her.
When the new clocks reached the end of their working life, BT ran a competition for a new voice, with a £5,000 prize.
Miss Simmons was on the panel of judges that chose Brian Cobby to succeed her.
On 2 April 1985 her last words on the clock were: "At the third stroke it will be 10:59 and 50 seconds", followed by Mr Cobby announcing: "At the third stroke it will be 11 o'clock precisely."
Mr Cobby - who still voices the clock - said: "Pat was a very sweet and charming woman.
"She was very gracious when she handed over the mantle... and I appreciated her support. She will be sorely missed."
The current Speaking Clock is accurate to within five milliseconds (five thousandths of a second).
BT says it is "about the size of a small suitcase", compared with the first clock which was about 8ft long.