Brighton's famous West Pier is about to be replaced by a piece of architecture just as daring as the original was 140 years ago.

In the week that councillors agreed to plans to build a 600ft viewing tower, the pier's official historian Fred Gray looks back at its exciting history and forward to its successor, the i360 or "Brighton Eye".

The 140th anniversary of the opening of the West Pier coincides with a critical decision by Brighton and Hove City Council to grant planning permission for the i360 and West Pier heritage centre proposal.

The past engages with a possible future and it's just the time to celebrate the contribution the West Pier has made to Brighton and Hove. Just why has the West Pier been so important to the city?

When it was designed and built it was a wonderfully modern and innovative structure, pointing the way for other pier designs over the next 40 years. It was the West Pier that really got "Oriental" architecture going at the mid-19th Century seaside.

The Royal Pavilion started it all 40 years earlier, but it was not until the pier made the first tentative steps to popularise Orientalism that the style spread around the coast to inspire endless seaside buildings, and then jumped overseas to mainland Europe and the USA.

The pier's designer was Eugenius Birch, the most famous of Victorian pier engineers.

The West Pier, for long Britain's only pier to be Grade I listed for its architectural importance, is usually seen as Birch's single most important and successful design. As English Heritage has recently said, the West Pier "was one of the most significant and characteristic of all Victorian buildings (and) a piece of Victorian engineering comparable to the great works of Brunel or the Stephensons".

This was the Victorians investing in new buildings for fast-changing seaside leisure. Many of the shareholders of the original West Pier Company were local people owning just a few shares. However, their faith in the future was sometimes put under pressure.

Pier design was an act of art as much as science. For all its grace and elegance the West Pier had design weaknesses. Less than two years after opening people fled from the pier when the structure "oscillated in an alarming manner" and seemed likely to collapse. Nature could also threaten the enterprise. A savage storm in December 1896 put paid to the older Chain Pier, with the wreckage washed along the coast to demolish the landward end of the West Pier, stranding several waitresses.

Getting a solid fix on the West Pier is difficult - it is a structure that has changed over time. Indeed, the pier was really built over a half a century.

The original 1866 open-decked promenade pier was rebuilt and redesigned into a pleasure pier with, by 1916, pier-head pavilion and central concert hall. Despite the five decades of building, part of the design magic of the pier was that it seemed a cohesive and organic whole. It is for this reason that the West Pier developed into a world famous iconic building - one that was instantly recognisable and that people wanted to visit.

In its pleasure pier heyday, the West Pier was a hugely popular palace of seaside entertainment visited by more than two million people each year. The acts and shows are all now long gone, but I'd have enjoyed watching Mazeppa, "the wonderfully intelligent talking and calculating horse", or seeing the comedy thriller, The Ghost Train, written by Arnold Ridley (later famed as Private Godfrey in Dad's Army).

Despite its success, the pleasure pier concept also faltered and by the Twenties new funfair attractions were added. This change was completed when the pier reopened after the Second World War. The theatre was converted into the Ocean Restaurant on the first floor - advertised with the slogan "lunch and tea over the sea" - and on the ground floor the Laughterland games pavilion with a crazy mirror maze, speedway racing, fairground stalls, and a juke box.

For all the joys of indoor entertainments, the sea was used in a variety of ways including paddle steamer excursions and swimming from the bathing station on the pier head.

Especially symbolic were the divers and aquatic entertainers. Two noted early West Pier divers were Professor Reddish and Professor Cyril.

Apart from their adopted academic titles both had a theatrical approach to their work. Professor Cyril was "the great exponent of High, Swedish and Fancy Diving".

In May 1912 he made the ultimate spectacular sacrifice, being killed while performing his "sensational bicycle dive".

Particularly well known later aquatic performers were Walter Tong, Zoe Brigden and Gladys Powsey. Zoe Brigden, from a Brighton family, was famous for her "wooden soldier" dive where with arms at her sides she plunged head first into the sea.

The last famous West Pier diver was the Great Omani - Ron Cunningham - who enlivened the pier with many spectacular performances during the Sixties.

These included the "death dive", based on an original Houdini act, which involved jumping into the sea from the pier head hooded, bound and padlocked.

By the Sixties all was not well with the pier nor, indeed, seaside Brighton. Trade ebbed away from both. Visitor numbers declined and the pier's income fell.

Ownership of the pier changed and, amid intense political wrangles, in 1970 the pier head was sealed off and closed to the public as being unsafe.

The pier head was threatened with demolition. The whole pier closed in 1975.

But the structure was saved through the actions of local people supporting the "We Want The West Pier" campaign.

Since then the struggle to save and restore the pier has been a roller coaster ride of hope and disappointment. But just as in the 1860s the pier is still "owned" by many local people through their membership of the West Pier Trust.

With closure and gradual decay have come myths, fantasy and increasingly polarised views. In one tragic story, boys died while working, diving into the sea, during the construction of the pier.

As far as I know the story is just that - pure fiction. Other people swear blind they visited the West Pier theatre after the war - again, it just did not happen.

There is also a little-understood natural history of the pier. A few lucky souls have peered under the Channel waters to the rich marine life inhabiting the undersea world. And above the waves there is another natural history of decay and erosion in a marginal and inhospitable coastal location, most dramatically revealed following the storms of the last few years.

But the destruction has also been by humans. Most starkly - and unless we believe in an immaculate conflagration - we should be aghast and horrified that the West Pier has been subject to two carefully planned and wellexecuted arson attacks.

Why? And why such abject failure to track down the perpetrators of the attacks?

The closed pier has led to contradictory responses both experts and people living in Brighton.

Some loathe it, others adore it.

This engagement - the way the pier almost forces us to take a view - is part of its importance and success.

It is remarkable how images of the derelict, storm-ravaged and burnt out pier pop up all over the place. Even the departure screens on Brighton Station display the outline skeleton of the pier head. The pier - even in its present state - is a wonderfully iconic structure locally, nationally and internationally.

Now in 2006 there are bright new plans for innovative buildings on the root end of the pier, in design as startling as the original pier plans 140 years ago. Of course there is no knowing what the future will hold, but the West Pier story seems unlikely to end just yet.

And for the present let's enjoy the fascinating and ever-changing views, according to the sea and weather, of what is left of an incomparable pier.

Take a virtual tour of the i360, go to the Brighton Eye video tour.