With the passing of Margaret Thatcher, we’ve lost not only one of conservatism’s heroes. We’ve lost one of the greatest figures of modern times, a woman who battled incredible odds to become prime minister, and then turned her country around after decades of decline.

I had the honor of working for Lady Thatcher in her private office from 2000 to 2002. Like anyone who has had that privilege, I had the opportunity to observe firsthand how fully she dedicated her life to serving her country. She was a true leader in every sense of the word, and Britain not to mention the world is safer, stronger and more secure because of it.

Well did Lady Thatcher deserve the nickname “the Iron Lady.” She displayed an iron will, to be sure, but she also possessed that great presence and spirit that made her a titan on the world stage.

Every time I visited Lady Thatcher, which I did for many years after she retired from politics, I found her to be cheerful and contented, with a clear spring in her step. Indeed, my former boss succeeded in outliving many of her own obituary writers.

They learned that Margaret Thatcher was someone you underestimated at your peril. You could never count the Iron Lady out.

Her concern for Britain, the “Special Relationship” between the United Kingdom and the United States, and the future of the free world remained undimmed throughout her life. It was always a deeply moving experience to meet with her, a figure of great conviction and principle, who had devoted her life to helping her country regain its position of leadership on the world stage.

For the current generation of leaders on both sides of the Atlantic, Lady Thatcher remains a role model of fortitude, principle and leadership at a time of economic upheaval and mounting threats to international security. Her great wisdom and example are sorely needed now as much as they were when she came to power in 1979.

It seems almost providential that her tenure in office would coincide with that of Ronald Reagan’s. The two of them worked so well together that they soon made the stagnation and malaise of the 1970s seem like a distant memory for both of their respective nations. By standing up to communism, they broke the back of the Soviet Union and brought the Cold War to an end without, as they say, firing a shot.

Lady Thatcher knew that liberal policies simply didn’t work. As she famously declared back in 1976: “Socialist governments traditionally do make a financial mess. They always run out of other people’s money.”

She won three general elections outright for a reason, and not just because the left was heavily split. It was because she offered a clear-cut set of policies based upon core conservative principles of limited government and free enterprise. Lady Thatcher understood the issues that Middle England really cares about: the economy, taxes, immigration, and law and order among them. She went to great lengths to support the creation of small businesses, while reducing burdensome regulations and cutting the level of business and personal taxation. She also understood the importance of maintaining and investing in a strong defense.

She offers many important lessons for today’s would-be leaders on the right. A conservative party can win, but only if it sticks to conservative values. Otherwise it becomes an empty shell that succeeds only in alienating its own base and destroying its very identity.

We will miss Lady Thatcher, but we remain hugely grateful for her example. Her legacy will serve as a living inspiration to conservatives all over the world.

-Nile Gardiner, a former aide to Mrs. Thatcher, is the director of the Margaret Thatcher Center for Freedom at The Heritage Foundation.