By HERE is a book which might just as easily be called Diary Of A Former Somebody. There was a period in London when the now-near invisible Sir Roy Strong appeared to be truly ubiquitous, popping up on every committee and at every social gathering in the city. His rise still looks meteoric, although it actually began with almost a decade of preparation.

In 1967, when these diaries begin, the former grammar school boy from north London had just been appointed, at the age of 31, to be director of the National Portrait Gallery. Strong's youth, as much as his non- establishment origins, was the subject of much comment and he capitalised on this by instigating a series of exhibitions and room refurbishments which kept both him and his gallery in the public eye.

The late 1960s witnessed his social and professional apogee; as these pages recall, he was taken up by a succession of admirers such as Cecil Beaton and Lady Antonia Fraser, delighted to discover an academic who was also an amusing dinner companion. Strong seems somewhat baffled by this attention, unable to see in himself what everyone else has spotted.

But he revelled in publicity, dressing up like a latter-day dandy and accepting every invitation which came his way. Although he could be - and often was - dismissed as a lightweight, the quality of his own publications (his speciality has always been late-Tudor and Jacobean iconography) gave Strong credibility in the museum world.

Thus, when the imperious Sir John Pope-Hennessy decided to retire as director of the Victoria & Albert Museum, the job went to Strong. Imagining that the charmed existence he had led at the National Portrait Gallery would continue in this new environment, his initial response was one of near ecstasy. However, the mood very rapidly changed and from 1974, when he took up his position at the V & A until the end of this book (when he resigned), the impression is one of near total gloom.

Strong's timing was unfortunate. He arrived in South Kensington just as recession hit Britain and this was followed by the premiership of Mrs Margaret Thatcher, who could never see any purpose in cultural affairs. Furthermore, there were intractable problems inside the museum, with both trade unions and senior members of staff traditionally at constant war with the director.

When Strong finally left, his successor, Elizabeth Esteve-Coll - who was to suffer even worse indignities than he - remarked: "This place has traumatised you." On the evidence of these diaries, such would seem to be the case. Even after a decade away from the V & A, Strong's sense of outrage at what he had to tolerate remains palpable.

Other than as an act of catharsis, it is hard to see what purpose the book serves. A certain number of old scores are certainly settled and Strong makes the most of every opportunity to demonstrate just what a hard- working and exemplary museum director he was. The pity is that, as published, his diaries really do have little other raison d'etre. Strong is not a natural diarist, as the erratic nature of his entries makes plain. He admits to sketchiness and often has recourse to a series of letters written to an old friend in the Netherlands. Only a handful of people come to life in his prose, with Princess Margaret regularly providing a star turn as an unhappy and demanding guest.

But unlike Beaton, among others, Strong's ability to sum up a social engagement or sketch a character in just a few lines is weak and he is prone to repetition; poor editing means that almost identical descriptions of the Queen Mother's drawing-room are presented on two occasions. It is rather dispiriting to see a writer describe his own work at one stage as "frankly an uninspiring read". To end as Strong does on more than one occasion: sad really.