The Bombardier headquarters and factory are pictured in Belfast on September 27, 2017. | Paul Faith/AFP via Getty Images Bombardier: Theresa May’s free-trade reality check Beneath the show of solidarity with Trump, the UK finds Washington is out to protect its own.

It was the day the U.K. government’s dream of a “very big and exciting” free-trade deal with the U.S. ran up against the brutal reality of international trade relations.

The U.S. Department of Commerce's decision to impose a punitive 219 percent tariff on the Canadian aircraftmaker Bombardier — potentially placing thousands of British jobs at risk in a Northern Irish factory that makes plane wings — was a textbook example of how a big player in global trade will often ruthlessly pursue its own interests and grind down smaller partners, even supposedly close allies.

Since the Brexit referendum, U.S. President Donald Trump and U.K. Prime Minister Theresa May have tried to rekindle the special relationship and talked up the prospects of a post-Brexit free-trade agreement.

But beneath the show of bonhomie, May's two attempts to deter Trump from an all-out assault on Bombardier counted for little. In the end, Washington rallied behind its own champion, Boeing, which accuses Bombardier of profiting from unfair Canadian and British subsidies.

May’s political enemies were quick to claim that the Bombardier case augured badly for the U.K.’s post-Brexit prospects. Trade experts added that the case also offered a sobering foretaste of how the U.K. will struggle to hold out alone in these kinds of disputes without the big guns of the EU, the world's biggest trade bloc, to support it.

“Do we really believe the U.S. will save us from Brexit with a comprehensive trade deal, when this is how they deal with fair and free international competition?” — Vince Cable, leader of the Liberal Democrat party

“Hard Brexit campaigners in government keep promising that Britain will get a great new trade deal with the U.S. after we leave the EU. That’s how they justify their ideological choice to leave the single market and customs union,” said the Northern Irish Labour MP Conor McGinn, on behalf of the pro-EU Open Britain campaign group. “But now we see the U.S. government taking a decision which is totally against our economic interests and could put thousands of jobs at risk across the U.K.”

May expressed “bitter disappointment” at the decision, as did Arlene Foster, leader of the Northern Irish Democratic Unionist Party, whose MPs are propping up May’s minority government in Westminster.

Vince Cable, leader of the pro-EU Liberal Democrat party, asked: “Do we really believe the U.S. will save us from Brexit with a comprehensive trade deal, when this is how they deal with fair and free international competition?”

The unions, generally anti-Brexit, weighed in too. “This should be a wake-up call to those who view the U.S. as our trading savior after Brexit,” said Frances O’Grady, general secretary of the Trades Union Congress. “The U.S. slapping huge tariffs on key U.K. exports is not a good sign of things to come.”

“International trade is dirty, that’s why we need rules” — EU official and former U.K. trade negotiator Chris Kendall

EU official and former U.K. trade negotiator Chris Kendall, who worked on the Uruguay round of the General Agreement on Tariffs and Trade in the 1990s, used his Twitter feed to offer an expert view on why the warning voices should be heeded, arguing that only very large economic powers could retaliate in kind against such protectionist measures such as those imposed by the U.S. against Bombardier.

"The EU has the weight to defend itself. We can retaliate. The U.K. acting alone can't take on the U.S."

“International trade is dirty, that’s why we need rules,” he said. “By advocating unilateral free trade, ‘liberal’ Leavers are bringing chocolate spoons to a knife fight. U.K. industry will be decimated,” he added, gloomily.

Some more recent U.K. government employees seemed to agree. “Bombardier a hard reminder that trade outside a regulated single market can be rough as well as dynamic. And U.S./Canada have [an] FTA,” observed Matthew O’Toole, until last month the chief press officer on Brexit inside No. 10 Downing Street.

Nick Macpherson, a former permanent secretary — the top official — at the U.K. Treasury said that while the U.S. "talks free trade" it more often “uses trade policy as an instrument of hegemony.”

Downing Street issued a statement Wednesday evening noting how the American decision had created an “uncertain and worrying time for the workers and their families at the Bombardier” facility in Northern Ireland. Defense Secretary Michael Fallon even went so far as to warn that the trade spat could jeopardize Boeing's future contracts with the British government.

That bad blood was a far cry from May’s boast, in her Lancaster House speech in January, that Britain “is not ‘at the back of the queue’ for a trade deal with the United States, the world’s biggest economy, but front of the line.”

In trade with the U.S., May’s opponents observe that America’s interests are really at the "front of the line."