Now online searchers can have at their fingertips every British phone directory ever printed
For the first time, aspiring genealogists can electronically search for forgotten relatives among 72 million telephone directory entries between 1880 and 1984. Experts say this will bridge a frustrating gap between the 1901 census and living memory, providing clues that lead to more traditional researches through the electoral roll and census.
Nick Barrett, a genealogist on BBC2's Who Do You Think You Are? and The Daily Telegraph's family detective, said: "This is a major breakthrough and will make research so much easier. You can search for lost grandparents by typing in a name or place.''
The first records to appear today on the website ancestry.co.uk are for London, Surrey, Herts, Essex, Kent and Middlesex, with the rest of the country following next year, with 250 million entries.
Tony Robinson, the actor and a spokesman for the site, which draws three million visitors a month, said: "[Directories] were always seen as either boring or so large and useless that strong men tear them apart.
"But I believe they will have enormous ramifications for how we see ourselves in the world . . . they will reveal our own small family dramas. We are at the birth of a brand new science.''
The resurrection of Britain's 19th and 20th century directories also offers a fascinating glimpse of an age before cold-callers, 11-digit numbers and the vogue for going ex-directory.
In 1910 Bram Stoker, the author of Dracula, was proud to be listed at Victoria 1436, and in 1925 callers wishing to contact Sir Winston Churchill simply called Paddington 1003, although they probably had to contend with a butler.
Almost anybody could track down the escapologist Harry Houdini in 1911, by calling Gerard 1312; Ivor Novello was to be found on City 1667 and Laurence Olivier was at Kensington 6505. Sigmund Freud and Marie Stopes were listed, as were Virginia Woolf, Benjamin Britten, Noel Coward, Lytton Strachey and Ian Fleming (call Tate 2300).
Viscount and Lady Astor had a number each, both in St James's Square, in 1920, while Sir Oswald Mosley was at Sloane 3395 in 1950. In 1961, before the Christine Keeler scandal broke, John Profumo could be called on Welbeck 6983.
But it is the apparent listing of the spy Kim Philby, in 1943, that shows how Britain was once a country where even those with most to hide need not be ex-directory.
"There is just something so exciting about finding the telephone numbers of famous and infamous people who would not be listed now, as well as relatives,'' said Josh Hanna, the managing director of ancestry.co.uk, which is believed to be paying BT pounds 25,000 a year for the right to use the directories.
"This is important and fascinating 20th century information that has been very difficult to find until now.''
The first telephone exchange opened in London in 1879, to be followed a year later by the first four-page directory, which listed names rather than numbers because so few people had a phone.
Callers hoping to contact the Royal Bank of Scotland, for example, just told the operator to whom they wished to speak and the call was connected.
By 1883, businesses were already being offered the opportunity to be ex-directory. But the idea was slow to catch on, with 588,000 people and businesses listed in the national directory by 1910 and 250,000 in London alone by 1924.
Telephone-owners are now more timid, with 60 per cent choosing not to be listed in the phone book this year, up from 37 per cent in 1997.
A BT spokesman said: "People seem to value their privacy more. I would be surprised to find a modern Kim Philby listed now.''