Andrew Scheer is off to London to start laying the groundwork for his pledge to negotiate a free trade agreement with the United Kingdom should he become prime minister.

The Conservative leader will use his four-day trip to begin "relationship building" with the U.K.'s Conservative government and promote the idea of a free trade deal between Canada and Britain.

Canada has struck a free trade pact with the European Union but that deal will no longer apply to the U.K. once it completes the process of extricating itself from the EU.

Scheer starts his four-day trip to the U.K. on Tuesday, beginning with a meeting with Boris Johnson, secretary of state for foreign affairs.

He'll also meet with Sajid Javid, secretary of state for communities and local government; Liam Fox, secretary of state for international trade; and Guto Bebb, minister of defence procurement.

He may also meet with British Prime Minister Theresa May, but that has not yet been confirmed.

Scheer will also take part Friday in a roundtable with business leaders, hosted by the Canada-U.K. chamber of commerce.

The trip comes just as U.S. President Donald Trump is flexing his protectionist muscles, promising to impose tariffs of 25 and 10 per cent on imports of steel and aluminum respectively and repeating his threat to rip up the North American Free Trade Agreement.

Putting ideas on the table

Jake Enwright, a spokesman for Scheer, said pursuing free trade now with the U.K. makes sense, both because it takes advantage of the "generational change" taking place in Britain as it exits the European Union but also because Canada needs to take concrete steps to reduce its heavy reliance on trade with the United States.

"It's important for us to show Canadians that we actually have a better plan to combat U.S. protectionist policies," said Scheer spokesman Jake Enwright.

"It's simply not enough really to criticize. We have to actually put some ideas on the table and this is one of them."

Scheer first announced his intention to pursue a Canada-U.K. free trade deal last month, in a speech to the Manning Conference.

In that speech, he called for "bold" action to diversify Canada's trade relationships.

"And I believe the first place we should look is to our cousins across the pond, who themselves are in a moment of generational change and newfound independence," he said.