It is almost impossible to avoid as the A27 turns from a dual-carriage way on the far side of the next hill, and the ordinary road winds downhill across the wide flat valley bottom, crosses the railway that comes straight down that valley, and finally just misses the town before the road winds uphill again through more trees and speeds away on double lanes.

I'd seen it passing through - more intent on reaching home for the weekend, but when my normal accommodation told me that they could not hold me for two days I determined to place myself a few miles up the road and use the evening to explore.

I lost the chance of exploring on my first evening, except by default. That is to say, I got lost and had not brought the map to locate the Travel Inn, so I drove around the tiny streets trying to spy the block. A garage finally told me that I had to travel out of town - it was beyond the trees on the hilltop. A Freudian block must have made me forget what I had seen repeatedly as the Inn stood on the road junction where I would have crawled past before. However, I was able to pass on the help of the garage attendant - as I came outside some Germans asked for the location of the Youth Hostel and I was able to direct them out of town to the road beyond the railway.

So I intended to see more on my final evening. On the hill the Castle stands to the northeast and to the southeast are the gothic spires of a church - the Catholic Cathedral. When I started to walk I found that they do not stand on either side of the hill but ancient and high stone walls curve around the whole north side of the town, like the inverted cup of a quarter-cup brassiere, and the mock-Jacobean post office and one side of the high street stand beneath the walls.

The Duke of Norfolk (he is also Earl of Arundel) had forgotten I was coming and had not left the great key under the drawbridge so I could not enter the castle, and I would have found it difficult to raise a mortgage to buy a ticket for the grounds and keep as well.

I quickly found this was one of those small towns that have grown in on themselves because they could not grow outside. The river is tidal and though it was low and flowing fast when I saw it, I could see moorings for what must be quite large excursion boats, and perhaps in the past too the sea flowed across that wide valley floor, flooding it and making it unfit for habitation. So buildings stood almost on building, and doorways were really entrances to yards where more shops and businesses were located.

The past is almost all this town's purpose - antiques shops, print and maps shops, artists' supplies, old-style grocers and family fruiterers lined the high street, and more were promised down the allies or on the three and four floors that rose above the ground.

The Castle grounds and walls merge into the Abbey, which seems to be a theatre now, and the parish church, which stands across the road from the great church that is now the Catholic Cathedral. The doors were closed, and I did not feel that the kudos I had once earned by moving a filing cabinet for the Catholic Bishop of Nottingham's secretary would open them, so I walked down the narrow streets which wound back down hill.

I thought there could not be anything to explore - but I was wrong, and pleased to be proved so. Amid the ancient cottages - though worth a fortune now - were scattered more and stranger businesses. There on the south coast I could see a room full of ice axes, crampons, kayaks and every other piece of paraphernalia I might want for Antarctic exploration. There was so much of it that the business had another shop down the road. On the other hand what the Dominican monks coming out after singing vespers would think of the lingerie shop beyond only the most bizarre mind might guess. They might be able more sense of the ARP wardens' helmets and stirrup pumps offered in the military history shop beyond, and perhaps they might take the icons and reliques to the restorers also located on the street.

Down by the river almost all the houses are new - though there was one I had to follow winding streets to study more closely after I had seen it across the car park of the deconsecrated chapel - a Georgian house whose two lower floors were missing, held up on stilt like walls at either side. I made a guess at a reason - I did not think that the original properties had been washed away.

In fact, like the towers of the filmic Rivendell, the ancient castle and cathedral are illusions. A Victorian Duke rebuilt the castle from ruins - it looks like what a castle should look like because it was built to look like that. The same Duke, like his descendant Duke a good Catholic, also built the church that only became a Cathedral in the reign of our own dear Queen. It is gothic because it was built in best Victorian gothic.

And the riverside houses? This is my reading. Arundel was a river port, like Gloucester and Chester, until late times. In the case of Arundel this was as recent as the 1930s. Now no docks remain and no warehouses - they must have become derelict and the houses replaced them – probably in the last twenty years. Looking at how the town has preserved itself, though, one can understand why someone should want to live there.

Unless events force it, I shall not go back, not unless I can once more explore - like a guide leading his party through their new lands.