The platform of the mighty Titan crane stands 150ft above the waters of the River Clyde just west of Glasgow.
It is surrounded by waste ground and the derelict buildings of a once-thriving industrial and trading neighbourhood.
This stretch of the river was, not long ago, teeming with merchant ships. It was a trading superhighway with global reach.
Britain hauled through this port endless shipments of wool and dried fruits from Australia, deep-frozen lamb and butter from New Zealand, steel from Canada, spices from India, tobacco from the Americas, sugar from the Caribbean.
Glasgow's confident imperial past is still written into the street names of the city - Jamaica Street, Plantation Square, India Quay.
For generations, Britain sat at the heart of a global trading block, in a system known as Imperial Preference.
It consciously chose to favour trade with the old “kith and kin” dominions of the Commonwealth and the colonies of the Empire, rather than with its European neighbours.
In the years before World War Two the Royal Family sat down each Christmas to enjoy their “Empire Pudding”, a dish that included at least one ingredient from each of the imperial territories - raisins from Australia, citrus peel from South Africa, cinnamon from Ceylon, sugar from Tobago.
In return, Britain sold to the Empire goods that were made in factories in the industrial heartlands.
From the top of the Titan crane, you can see the site of the old Singer sewing machine factory that once employed 17,000 people and the former home of John Brown Engineering at Clydebank - as well as the shipyards that launched the great ocean-going liners Queen Mary, Queen Elizabeth and the QE2.
From a plant in Springburn, tens of thousands of steam locomotives were hauled down to the docks by Clydesdale horses to be loaded into the holds of ships bound for India, Malaya, Egypt and beyond.
Now the Titan crane - once one of dozens on this stretch of the river - stands alone, unused save as a tourist attraction, a forlorn echo of a lost age.
Imperial Preference was a system of trade protected by import tariffs and preferential trade agreements, and reflected a generations-old British policy to steer clear of European alliances and commitments.
“If Britain must choose between Europe and the open sea,” said the country's wartime Prime Minister Winston Churchill, “then she must always choose the open sea."
But after WW2, the system was sailing on borrowed time.
As the Empire fell apart, so too did the trade. The great port cities of the west coast went into steep decline.
Right up to the 1970s, in terms of the volume of overseas trade it handled, Liverpool was the second busiest port in the UK after London.
The Mersey, like the Clyde, connected Britain to the wealth of the entire world.
In the 1960s, Britain made the historic decision to seek membership of the European Economic Community. The Treaty of Accession - signed by the Conservative Prime Minister Edward Heath - came into force on New Year's Day 1973.
“Liverpool found itself in the wrong place, on the wrong side the country," says Prof Nick White of Liverpool John Moores University.
“In the 1980s, Liverpool was known as the 'Bermuda Triangle' of British capitalism, as trading companies and manufacturing firms left, and moved south and east, to ports that were much more oriented to Europe. Its trade was with parts of the world that were increasingly politically unstable or economically stagnant. The high-value trade was now with Western Europe.”
Many in the old “kith and kin” dominions - especially Australia and New Zealand - saw this huge shift as a betrayal.
Close to 90% of the lambs reared in New Zealand had, traditionally, been shipped to the UK. Now the produce of the Commonwealth countries faced punitive import tariffs imposed by Europe.
Australia and New Zealand began the painful process of re-orienting their economies to face not Europe, but Asia. The UK's decision to enter Europe changed the shape of trade on the other side of the world.
Britain's mercantile economy changed shape too. The transition from Empire to Europe sucked the economic life from the great port cities of the west and moved the country's economic centre of gravity south and east.
A different kind of economic activity would thrive in the age of Europe. European membership accelerated a process that was already under way - the decline of traditional manufacturing, especially heavy industry, and the rise of a service-based economy.
The manufacturing that survived would now be much more closely integrated with the economies of Europe than ever before.
Gestamp Tallent is a Spanish-owned company with plants across the North East of England and the Midlands. It also has factories in 10 EU countries and a further 10 outside the EU.
At Newton Aycliffe in County Durham it makes highly specialised parts for cars - mostly components for suspension mechanisms.
This is not the crashing industrial turmoil that once fuelled the economies of Clydeside and Merseyside. This is high-end, high-value, high-tech, high-quality precision engineering - and, crucially, it's located further east, in the part of the country that faces Europe rather than Winston Churchill's open seas.
The story of Gestamp's Newton Aycliffe plant is a revealing commentary in what has happened to the UK's economy in 40 years of EU membership.
It began in 1948 as a British company making fancy goods such as make-up compacts. In 1980, seven years after the UK entered the European Economic Community, it had a turnover of about £3m a year.
By 1990 that had risen to £30m - a tenfold increase in 10 years as the company grew more highly specialised and went upmarket in the value of goods it was manufacturing.
It was bought first by the German company Thyssen-Krupp, which, in turn, sold to the Spanish-owned Gestamp.
Today, the sales of just the Newton Aycliffe plant are more than £200m a year.
The factory has recently bought two vast multi-million pound steel presses capable of taking a flat piece of steel and putting it through up to eight separate processes in less than 25 seconds.
It spits out one of these components every three seconds, and the plant operates on three eight-hour shifts around the clock, night and day.
And the market for these products?
Two-thirds go directly abroad - mostly to plants elsewhere in the European Union where the cars are assembled. Gestamp has factories from Portugal in the south to Sweden in the north.
Only a third of what Gestamp makes is sold to car plants in the UK, but much of that ends up in European exports too, in Nissan and other UK-assembled cars that are bound for the export market.
“Our equipment, we buy from Europe,” says Clive Wheeler, who runs the Newton Aycliffe plant. “Our raw materials come from Europe. And what we make we sell to Europe too.”
Would a vote to leave the EU threaten economic activity like this? Much of British industry certainly fears so.
But pro-exit campaigners say emphatically not. They say it will be in the interests of the other EU countries to go on trading with the UK - and that nations can, and do, trade freely with Europe from outside the EU.
To see how the shape of Britain's mercantile economy has changed in these four decades, go to Southampton docks. Its 210 acres are piled high with tens of thousands of containers.
It handles over a million tonnes of bulk cargo a year. It has 30 acres of above ground storage for cars and other vehicles, and is now the UK's leading port for car import and export. It can load and off-load four full-size ocean-going cargo ships simultaneously.
In 1973, the container port barely existed.
The visual contrast with the lonely vigil of the Titan crane at Clydebank outside Glasgow, surrounded, as it is, by the dereliction and wasteland of the old docks and shipyards and heavy engineering plants of the Clyde estuary, could not be more stark.
It is the story of Britain's transition from the age of Empire to the age of Europe.
This is what the EU has meant to Britain over the decades - trade. It is why the prime minister we associate most strongly with Euro-scepticism, Margaret Thatcher, was in fact the prime minister who took the UK deeper into the European embrace than any other British leader.
In 1986, when she signed the treaty that created the Single European Market, she did so because she saw it as a triumph for trade unhindered by government - as Thatcherism on a European scale.
Yet within a few months she was also warning that an emerging European superstate, unaccountable and unelected, now posed a threat to the sovereignty of elected national parliaments.
In the 1980s, the European Economic Community went through its second major expansion.
The UK, Ireland and Denmark had joined in 1973, bringing the number of member states to nine.
All three of those states were old and settled democracies, with entrenched traditions of multi-party politics, free economies and the rule of law.
That was not so for the three nations that joined in the 1980s.
Portugal, Spain and Greece - Europe's “southern tier” - joined the European Economic Community as part of their transition from right-wing or military dictatorships and highly insular and state-controlled economies.
All three were committed to joining the European mainstream as a way not just of gaining access to European trade, but of modernising their entire countries.
They saw it as a way of entrenching democratic practice, freedom of speech, the rule of law, parliamentary government and a free press.
For them, joining the “European family of nations” was not just about trade, it was about emerging from the darkness of oppression and dictatorship.
That connected them very strongly with the founding ideals of the original six.
When France, Germany, Italy, Belgium, the Netherlands and Luxembourg signed the Treaty of Rome in 1957, the driving motivation was not economic but political.
They believed that by binding the economies of Europe tightly together, they would make war between the European powers not just undesirable but impossible.
Economic integration was, for them, not the end in itself. It was the means to an end. And the end was not economic but political.
Europe's third major expansion came 15 years after the fall of the Berlin Wall.
Ten new nations joined in 2004, eight of them former communist states in Central and Eastern Europe.
They too associated EU membership with goals far loftier than free trade. The European Union did too, and in a formal sense.
It drew up a set of criteria that states would have to meet to qualify for membership. These were adopted at a summit in Denmark in 1993, and are known as the Copenhagen Criteria.
They go way beyond the rules of free trade. The post-communist countries were told that they would have to achieve stable democracies, the rule of law, human rights, and the protection of minorities.
More than water separates Britain from the European mainland. Historical experience does too.
Almost all of the continental European nations have suffered - within living memory - the humiliations and privations of military defeat, foreign military occupation, and fascist or communist dictatorship.
For them, the European process has been a means to turn the page on that dark past. It's been about democracy, national and individual freedom. It's been about national redemption.
That has never been so for the UK. The British did not see foreign flags flying above their national citadels, nor foreign troops marching down the avenues of their biggest cities.
The British did not seek European integration as a way to entrench a battered democratic tradition, or to redeem a shameful chapter in their history.
When the original six first formed the European Coal and Steel Community in the 1950s, the then British Prime Minister, Clement Attlee, is said to have remarked that its members “consist of six countries, four of whom we had to rescue from the other two”.
In 1956, when those same six met at Messina in Italy to start negotiations to form the first European Economic Community, Britain was invited to join them. There is still a document in the National Archive at Kew on which the then Foreign Secretary, Harold MacMillan, has scribbled a note in the margin: “Tell them I'm busy with Cyprus.”
Modern Britain has been shaped by its European membership.
After the Empire fell apart, Britain embraced the economic opportunities that Europe's recovery after WW2 presented, but it has never loved the political obligations that came along with those opportunities and which, for many of the European partners, were the main purpose.
The English Channel has been a barrier that has shaped the destiny of Britain. And it remains a border separating two quite different ways of thinking about the EU, and what the EU is for.