AS a boy I had a thing about walls. Just like most kids I would make a beeline for those I could climb, walk along and sit on top of. Unlike other kids, though, it became a bit of an obsession for me. Later it would lead to a passion for mountaineering, but well before then it simply got me into all kinds of trouble.

Like the time when I was 12 years old and rigged up an improvised abseil rope to lower myself off the wall of a 30 foot railway bridge, only to then press gang my younger brother into doing the same despite his tearful protestations. Needless to say my parents were none too pleased.

Above all, walls brought out an insatiable curiosity in me as to what lay on the other side. Another childhood escapade resulted in me clambering over the top of one lined with shards of broken glass to raid the apple trees in a small orchard.

It was only when myself and a pal dropped down into the orchard that I realised the owner also bred German Shepherd dogs that he let roam free in the grounds. Suffice to say our rapid escape was a painful and bloody experience, but it still didn’t quell my curiosity.

That’s the trouble with walls, even though they are almost invariably meant to keep people out or in, almost always we will want to see what lies on the other side.

US president Donald Trump doesn’t seem to realise this, of course, as he continues to bang on about the need for a border wall with Mexico.

That the terrorist and migrant excuses he uses to justify the building of such a wall is largely a fabrication barely matters. Even if he were to exercise his emergency powers threat and find the

$5.7 billion to build his wall, people will always find a way to circumvent it.

Walls almost always represent division and I for one have never been sympathetic to the notion of enforced division among people. The desire to break free of restrictions on movement or incarceration is deeply engrained in the human condition. Ask South Africans once forced to live in Bantustans or Palestinians today in Gaza.

Thirty years ago I was to witness for myself how powerful that desire can be as I watched the collapse of the Berlin Wall.

Along with an American colleague, I was sitting in a bar off West Berlin’s Kurfurstendamm district on November 9, 1989, when news broke that those who had lived either side of the wall decided enough was enough and the time had come to end that division.

In the hours that followed, thousands swarmed around Berlin’s checkpoints trying to cross the barrier that had separated East Germans from the world for the previous 28 years. Bewildered border guards could only look on helplessly as the Berlin wall was finally breached.

On Bornholmer Street, I watched as crowds sang, drank, hugged. No blue shirts of the East’s Free German Youth on the streets now: just free youth.

Chants of “Wir sind das Volk,” – “We are the people” – echoed around the streets, as did the sound of alpine horns.

In the hours that followed, “Ossies” and “Wessies”, East Germans and their Western counterparts, would come together in one massive celebration.

Yet more than three decades after the Iron Curtain came down, walls have been going up again, and long before Trump there have been numerous advocates for the building of walls.

How many people, I wonder, know for example that one of Israel’s own prominent military historians, Professor Martin van Creveld, of the Hebrew University, who was the first to propose a wall round the West Bank, drew his inspiration for that same proposal from the Berlin Wall, after spending a year’s sabbatical in Germany in 1980-81?

“If I could, I would build a concrete wall so tall that even birds could not fly over it, and above all, so the people cannot look each other in the face – complete separation,” Van Creveld is quoted as saying in an article, some years before Israeli prime minister Ariel Sharon took his idea to heart and made the wall a bitter reality for those Palestinians who now live in its shadow.

Of course, whenever questions about the legality of Israel’s wall are raised, its leaders invariably respond with the same answer: “It stops the bombers and that’s all that matters.”

But how can Israel insist on calling it a “security wall” when instead of just separating Israel from the West Bank, it separates Arab from Arab?

Indeed, how could people whose history is full of terrible ghettos now be building one themselves?

For some Israelis there is simply no debate to be had. That much in common they share with Trump.

As far as they are concerned, the crushing effects of the wall on the lives of millions of Palestinians is a small price to pay for the relative guarantee of their own personal security.

But to call it this way makes for a convenient defence of a policy they also know is little more than a land grab and indefensible in terms of international law.

“If you want security for your house, you build the wall in your own garden, not in your neighbour’s,” I remember a Palestinian shopkeeper telling me near East Jerusalem, where the wall had cut his business off from the village customers who gave him a meagre income.

He had a point and thinking of Trump’s obsession with the Mexico border wall his words remind me too of those lines in a poem by the great American writer Robert Frost:

Before I built a wall I’d ask to know
What I was walling in or out,

And to whom I was like to give offence.
Something there is that doesn’t love a wall,
That wants it down.

Across the world, in concrete and steel, with watchtowers and barbed wire, the wall builders remain determined to divide communities and countries, halt refugees and separate rich from poor.

History has shown us that walls never have and never will be the answer and that only dialogue succeeds.

It’s to its credit that Scotland sees no need for such barriers, be they Brexit-induced or motivated by a xenophobic wish to slam the door on those who want to make this nation their home. Bridges, not walls, must always remain the way we engage with the world.