What could the upwardly agile of the Eighties not be without-along with their mobile phone, Golf convertible, wharf conversion and negative equity? The Filofax of course. But surprisingly, perhaps, this little bible of "essentials and trivia" wasn't born in that decade. Last week it turned 75.

To mark the occasion the company is producing a limited edition of 1,921 (get it?) burnished calf-leather, dual gilt-mechanism Filofaxes (a snip at pounds 500), complete with cream 18-month diaries and other delights. The commemorative design is based on one of Filofax's earliest incarnations: a diary owned by Grace Scurr, who started at Norman and Hill (now Filofax) as a temporary secretary. When the company's offices were blitzed during the war, it was Grace's diary, in which she had recorded customers and suppliers, that literally saved the firm. And it was Grace (who went on to become Chairwoman, retiring in 1955) who coined the name Filofax - "a file of facts".

The original idea was based on an American organiser system, Lefax of Philadephia - loose leaf information sheets on technical matters and trade information, for practical and flexible reference. Filofax came quietly but firmly into British life, used mainly by journalists, lawyers, doctors, soldiers and clergymen. (The Rev Geoffrey Cox has been using a Filofax since the year Grace Scurr retired, making meticulous notes for sermons in his perfect handwriting; his filofax was on display at the celebration of the anniversary at the Design Museum in April.)

However, the reason we think of the Filofax as an Eighties icon was its boom during the decade. David Collischon, a life long Filofax fan, set up a business in 1976 to market Filofax by mail order, and went on to acquire the company in 1980. In 1987 he brought Filofax to the Unlisted Securities Market, valued at pounds 12 million. It is now valued at over pounds 30 million and sells in over 40 countries worldwide. Filofax, like the Hoover, has become synonymous with its genre.

It also became a style icon whose cool was indisputably established when fashion guru Paul Smith placed a black filo in his shop window alongside a Montblanc pen. But it was a style of tradition, not of hi-tech. The fast growing hi-tech alternatives, the so-called Palm Tops, headed by Psion with their 3a series, are the new pocket computer life support systems. The Psion seems to do everything short of making your bed and bringing you a cup of hot cocoa at night. It has an agenda, database, word processor, spread sheet, calculator, international clock, automatic telephone dialling, and an alarm which can be programmed to wake you up to the "sound of a loved one", bleep you with a message or tell you it's time to go to that meeting. You can attach it to your PC, print out, fax out, even phone out short messages. All kinds of software can be added from language phrasebooks to games (users tell me that HomeRun, the card "patience", is addictive). Hewlett Packard has recently brought out competition in its HP Omnigo series. Apple even marketed a computerised notepad that can recognise your handwriting, though not many had the patience to sit down and teach it.

Is the classic personal organiser threatened by these thoroughly modern models? According to W H Smith it is only at the top end of the range - executive classic organiser versus, say, the Psion - that sales are being affected. There's still as strong a market for the average personal organiser as for the mid-range electronic ones, such as Sharp or Casio which start at pounds 29.99. The Psion 3a1 and 3a2 - one or two megabytes of memory - sell for pounds 339 or pounds 399.

Filofax is however responding to the digital dream by researching its own electronic database to add as an insert. The manufacturers of the Seven Star diary, the Dutch equivalent of Filofax, has already created a digital planner to insert in its 1997 diary. This quiet little winner from The Hague is even older than Filofax and was started by a certain Peter Schreuder just after the First World War. It's definitely worth a look. The day by day diary pages include quotations to keep up morale - "There is nothing permanent except change" or "Only men of small stature go chasing after titles" or, best of all, "A woman needs a man as much as a fish needs a bicycle". Now that's what I call progress.

Limited Edition Filofax, available from the end of June from Harrods, Selfridges and The Filofax Centre (0171-499 0457)

For details of the classy new range of Filofaxes call 0171- 432 3028.

Dutch organiser at Success of London, 60a, Crawford St, WlH 1HS tel 0171- 723 0738

Filo facts

One million Filofaxes are sold each year. No one knows exactly how many inserts are sold to accompany them. What we do know is that the designers responsible for these useful inserts have been nothing less than inventive. How else do you explain the following offerings?

Filofiction: scaled-down, hole-punched novels which slipped easily into your trusty Filofax. The first author to have their work jostle alongside City whiz-kids' bulging diaries, address books and financial planners was Jeffrey Archer, with Not a Penny More, Not a Penny Less.

Pregfax: launched in 1990, this was an insert designed for the woman trying to have children. It came with a guide to gestation, charts and diet sheets as well as the all important nursery planner.

Gerryfax: a jolly insert aimed at the older man or woman for recording bridge sessions and bowls.