I fell deeply in love with Oxford the day I arrived from South Africa 35 years ago. Now I think of Oxford as a sort of ideal world; my judgment is clouded by the fact that when I arrived there I was very young and everything was possible. But still, every time I go to Oxford, I fall in love again. One of the things I love most is the knowledge that under the streets leading from the Bodleian Library are millions of books and manuscripts, most of them in miles of shelving deep underground. As you walk along Broad Street you are passing over one of the greatest collections in any library anywhere - not only are there the millions of books that have been deposited since the 17th century when the library became a library of record, but also 10,000 medieval documents, the priceless collections of Islamic, Chinese, Indian, Japanese and Hebraic works and - surprisingly - a collection of ephemera, from bus tickets to advertising posters, recording the tastes of the early 20th century, and the world's most extensive collection of musical scores and bills relating to the Jazz Age in the US.
Somewhere in the library, closely guarded, are unique treasures, among them the first edition of Franz Kafka's The Castle, the original score of Gustav Holst's The Planet Suite, a quarter of all the existing Magna Carta documents dating from 1215, the oldest known copy of Shakespeare's First Folio, which was deposited straight from the printers, and the earliest known copy of La Chanson de Roland, the 11th century French epic poem. I have been lucky enough to see all of these. Increasingly they are being put on public display.
What you see above ground is what Yeats called the most beautiful library in the world. It's made up of a number of buildings, the oldest being the Divinity School dating from 1435 and above it Duke Humphrey's Library of 1487. The Radcliffe Camera is an 18th century building, set in the most beautiful square in Oxford, bounded by the main library quadrangle on one side, All Souls College on another, Brasenose College on the third and the original cathedral church of Oxford, St Mary's to the fourth. On Broad Street is the elegant Clarendon Building designed by Nicholas Hawksmoor. The Divinity School, no longer used for teaching, has an astonishing carved stone roof, a masterpiece of medieval craftsmanship. Don't miss it.
As I walk that way, I believe I hear, like the noise from a power station, the humming of hundreds of years of study and thought, and it always fills me with joy. The overwhelming fact about Oxford is that not only are the colleges in their mottled stone astonishingly, even heart-stoppingly, beautiful, but that the place radiates a kind of excellence and tolerance which has come to stand for the essence of England. It has a reputation, thanks largely to the 1970s television production of Brideshead Revisited, of being the home of the idle upper classes. This is the myth of Oxford, long out of date, which still clings to the place. In fact it is now a great research university, with increasing numbers of graduates and is consistently voted one of the top two or three universities in the world. But it is true that the colleges are often magnificent with the occasional candlelit dinner in splendid halls with all the fellows in gowns at the top table. In a tradition that is unique to Oxford and Cambridge, students are admitted not to the university, but to a college, which will be their home and the focus of their loyalty. Most undergraduates will write - the figures show - 1.7 essays a week, for close scrutiny by a tutor, quite often one to one. There is no escaping.
For the visitor it can sometimes be difficult to gain access to the colleges, but they are all open at some time or another and it is worth checking their websites for the relevant information or the general college information website. Most of the colleges have wonderful gardens, from the 100-metre herbaceous border of Trinity, to the deer park of Magdalen. There is, however, no consistency of opening times. Christ Church is the most magnificent college in Oxford and it is an absolute must for any visitor. There is a wonderful view from Christ Church over the meadow that leads down to the Thames, known as the Isis within Oxford. Another river, the Cherwell, joins the Isis downstream. In Christ Church the college porters still wear bowler hats on high days and holidays, and here in its vast Tom Quad you can certainly get a sense of Brideshead. There is a truly astonishing hall and its art gallery would make any medium-sized city proud. Most of the colleges have endowments: St John's is in fact far richer even than Christ Church, and owns, among many other bits of real estate, Bagley Wood on Boars Hill south of Oxford, a largely ancient woodland full of birds and deer. Magdalen College has the loveliest garden of all, including the deer park and its one-mile Addison's Walk around an ancient meadow, which in spring bursts into flower with a million fritillaries. Many an academic has walked this way, pondering deeply.
Oxford is surrounded by water, and one of my favourite walks is out to Binsey, striding out over Port Meadow, common land, and crossing the Isis by a bridge, passing what is probably the last farm in Oxford itself, to arrive finally at the lamplit, unheated, atmospheric little church, which stands next to the treacle well that inspired Lewis Carroll. The Oxford Parks - so called because two parks were combined - is another favourite, bounded by the Cherwell. The botanic gardens and Merton Fields are also skirted by the river and in summer always the scene of plenty of hilarious and inexpert punting. Punts can be hired from the two main bridges, Folly Bridge to the south and Magdalen Bridge to the east.
Since my days as a student, hotels and restaurants in Oxford have all improved beyond recognition. The Mogford family own the sleek Old Bank and the atmospheric Old Parsonage hotels, both with excellent restaurants, Jamie Oliver has his Jamie's Italian (no booking) and in the area known as Jericho, there are lots of fairly reasonable and good restaurants, including Freud and Brasserie Blanc. Around the old prison, now redeveloped, there are plenty of serviceable chain restaurants.
Oxford is in some ways a secret place. The colleges face inward, the buildings are not signed, but it is a place that is full of wonderful surprises. Above all, Oxford is one of those places that stands for something way beyond its physical presence. It is not by accident that Oxford is synonymous with excellence and is known as one of the world's great brands. Justin Cartwright's memoir Oxford Revisited is published by Bloomsbury. For information on visiting Oxford University, visit www.ox.ac.uk/visitors