During his first Christmas as a married man, his wife Laureen gave him an autographed copy of Thatcher's memoirs, Harper recalled, describing the Iron Lady as a role model both for Conservatives and for women.
"She was ... one of the very first prominent women leaders and has, I think, been an inspiration for all women in conservative parties across the world and certainly in our own Conservative party in Canada," he said.
"As you know, we're now seeing — particularly this generation — just an explosion of women achieving high leadership positions across Canada and other parts of the democratic world and she was really a path-breaker in that regard."
Thatcher, who died last Monday at the age of 87, will be given a funeral with military honours at St. Paul's Cathedral on Wednesday.
The guest list includes members of the political and intellectual elite from around the world, as well as British cultural royalty like singer Shirley Bassey, composer Andrew Lloyd Webber and author Jeffrey Archer.
The cathedral seats about 2,300 and is expected to be filled to capacity. A much smaller group of prominent Conservatives gathered Tuesday night to toast Thatcher on their own.
Hosted by current British Prime Minister David Cameron at 10 Downing Street, the guest list included former U.S. vice-president Dick Cheney and former Australian prime minister John Howard, among others.
Harper was also a guest at the dinner, finding himself for the first time in many years at private event with another notable Canadian conservative: Brian Mulroney.
Much of Thatcher's time in office overlapped with that of Mulroney, who was prime minister of Canada from 1984 to 1993. Thatcher served from 1979-1990.
The two butted heads, most notably over applying sanctions against apartheid-era South Africa: Mulroney supported sanctions while Thatcher did not.
During her time as prime minister, she acquired the Iron Lady sobriquet for her strong opposition to the Soviet Union.
Harper said her legacy as a champion for freedom and democracy still resonates for conservatives.
"(She) was instrumental in the fall of communism, the transformation of the world towards really the democratic model," he said. "We have a long way to go in the world, but it is now the model to which virtually all of mankind aspires."
Thatcher also upended the British economy in the aftermath of the recession of the 1970s, taking a strong stance against organized labour and swiftly privatizing national companies.
Her economic policies led the way for conservative governments of the future, Harper added.
"She was one of the people who rediscovered the importance of conservative economics, made it the force it became throughout the world, leading to globalization."
The subject of the global economy was one of several Harper touched on Tuesday in a short meeting with Cameron before the dinner, according to the prime minister's office.
The pair also discussed the ongoing Canada-European Union free trade agreement.
Security in London on Wednesday is expected to be even more robust than originally planned in the wake of Monday’s twin bombings at the Boston Marathon.
Though not an official state funeral, Wednesday's service is expected to be the grandest seen in Britain since the 2002 death of the Queen Mother.
It will be the first prime ministerial funeral attended by the Queen since Winston Churchill's in 1965.
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