The first time I met Ravi Zacharias I was doing postgraduate work in theology and hoping to one day serve the Lord with apologetics. Our mutual friend Michael Ramsden invited my husband and me to have dinner with Ravi and we found ourselves sharing an Indian meal and conversation that would change the trajectory of my life.

I remember laughing a lot. Time with Ravi always meant that – his sense of fun was never diminished by the stresses of work or travel. But Ravi also asked a lot of questions. Questions about my research, about theology and about our then recent trip to meet some leaders of Afghanistan's Taliban. Ravi Zacharias took an interest in people. He approached life with a tremendous intellectual curiosity but that never detracted from an unusual ability to connect with people.

Ravi was born in Madras (now Chennai), India in 1946 to nominally Christian parents. His great-great-great grandmother had converted to Christianity from Hinduism and suggested that the family name be changed to Zacharias. But Ravi himself was a reluctant cultural churchgoer until he heard the gospel as a teenager and was the only person to walk forward at a Youth For Christ outreach event.

He was not a particularly studious young person – preferring batting at the cricket crease to burying his nose in books. But at some point, as a 17-year-old he became overwhelmed with despair and attempted to end his life. It was in hospital recovering from the effects of that attempt that a YFC leader brought him a Bible and the adolescent Ravi heard the words of Jesus: "Because I live you also shall live" (John 14:19). Ravi quickly grew as a passionate Christian and found his voice as a young preacher.

The passion with which he preached was pretty astounding and for me, this is what marked Ravi Zacharias out. It reminded me of the stories of George Whitefield, who was frequently moved to tears while preaching. Ravi didn't often weep but the sense of the raw power of God flowing through his anointed words was a joy to behold. While he often introduced quite complex philosophical thoughts and reasoned arguments in his presentations about Christian faith, he did not hold back in the pulpit or at the university lectern. He was not afraid to express passion in his delivery.

The urgency of the truth of God's love for his world, the lostness of humankind without Christ, the emptiness of materialism and the reality of the resurrection of Jesus triumphing over death pulsated through his preaching. Perhaps that's why thousands and thousands of people flocked to hear him all over the world, regardless of their religious or cultural background.

Right up until February of this year, Ravi was preaching in Sri Lanka to a large crowd of pastors and leaders. Ravi often spoke for over 40 minutes on subjects like the problem of evil or the search for meaning or the uniqueness of Christ. As popular consensus told us that young people can't concentrate for prolonged periods of time, Ravi preached to packed-out audiences in pin-drop silence. Many of his hearers were the young, teenagers and students figuring out life's big questions. His messages combined profound philosophical insights, multiple literary allusions and straightforward explanations of the Christian gospel.

For Ravi questions lead us towards God and not away from him. He was not afraid to explore the deepest and hardest questions facing the world and to set forth how Christ meets humanity there. He was utterly confident that the Christian faith had profound meaning to offer in the darkest shades of the soul.

Perhaps even more surprising than the intricately prepared and intellectually challenging messages was the fact that without fail he opened himself up to live Q and A. At the turn of the millennium, Ravi gave a series of lunchtime talks for University of Oxford students hosted by the Oxford Inter Collegiate Christian Union. People queued up in Pembroke Street to get into St Ebbe's Church every day for a week to hear him speak but crucially to ask him their questions. I noticed that there were many tears that week as sceptical students found their way to faith in Christ.

In the book of Acts, after Paul speaks in Athens at the Aeropagus, Luke comments that "some sneered, but others said, 'we want to hear you again on this subject'" (Acts 17:32). Ravi did not insulate himself from the sneers of those who regard belief in God as foolish; in fact, he often stayed after the formal Q and A time speaking one to one with young people, helping them grapple with their questions about God and introducing them to a God who can be trusted, who is real, who is good and who can be known. Ravi notably gave a similar series of talks on the campus on Harvard University for the first Veritas Forum in 1992 and those lectures became the basis of his bestselling book Can Man Live Without God?

It takes courage to stand up in some of the most elite institutions of learning in our world, whether that be on the campuses of Yale, Princeton, and Zayed University, and invite questions. Where did that courage come from? Ravi himself did not have an Ivy league education to draw on. He (and later, his parents) emigrated from India to Canada in 1966. And whilst working after hours in low paid jobs to pay the tuition fees, he attended Ontario Bible College where he obtained his Bachelor of Divinity and later Trinity Evangelical Divinity School in Illinois, where he obtained his Master of Divinity.

Ravi dedicated his life to reading and studying – the great literature of the world, classical, analytic and European philosophers and a great deal of theology. He often spoke of his sadness that he had not had the means or opportunity to take a doctoral programme and that is why he so generously invested in the lives of young apologists doing PHD studies, and young and gifted ministers seeking direction and mentoring.

So, where did his courage and confidence rest if not in academic accolades? First and foremost, his trust was in Christ. He had a devoted personal commitment to Christ and a deep life of prayer and studying the scriptures. But I believe that the muscles of his courage were also profoundly shaped by his early preaching tour of the Far East. In 1971 as a 25-year-old Ravi went to Vietnam where he preached up and down the country to US military personnel and to captured Vietcong members. On various occasions he barely escaped with his life. The scale of the response to the gospel in that time and in a further trip in 1974 to Cambodia, built a confidence in him that it is God who rescues and saves, and that the work of the evangelist is a calling from God. And Ravi Zacharias was an evangelist to the end.

Billy Graham recognised this and invited Ravi to address his inaugural International Conference for Itinerant Evangelists in Amsterdam in 1983. Before 3,800 evangelists from 133 countries, Ravi gave the riveting message "The Lostness of Man." He explored how pleasure, technological advances and economic prowess had not been able to deliver the promised meaning and happiness humanity was seeking. This talk launched Ravi onto the international stage and took his preaching ministry to a wider and wider audience. A year later his organisation, Ravi Zacharias International Ministries, was launched.

Ravi had met his wife, Margie, nee Reynolds, through their church in Toronto. After two years of knowing one another, her parents gave permission for them to date and they married in 1972. RZIM was very much a joint calling and Margie served alongside Ravi in the ministry in many different capacities, notably helping him with the editing of his books and championing the evangelistic focus of his calling.

Evangelism remained his greatest calling. Even in early May, when Ravi was discharged from M. D. Anderson Cancer hospital in Houston, Texas so that he could end his days at home with his family, he was sharing the love of Christ and the good news of the gospel with the medical staff that had been looking after him.

Ravi's understanding of Eastern culture and Eastern religions enabled him to speak and write Jesus Among other Gods – another of his bestselling books. He had an outsider view of Western questions of meaning so often influenced by pluralist or New Age thought patterns. He was able to apply his cultural and intellectual understanding in such a way as to connect both with Easterners and Westerners, always pointing his hearers to Jesus Christ crucified and raised from the dead.

His respectful approach meant that he was invited to speak in unusual settings for an evangelical preacher. It is noteworthy that he spoke at the Lenin Military Academy, Moscow in 1992, a bastion of communism during the Cold War. He was hosted by His Excellency Sheikh Nahyan bin Mubarak Al Nahyan in Abu Dhabi, United Arab Emirates in the Middle East in 2019, and he was the first evangelical since D. L. Moody to be invited to address the Mormon Tabernacle in 2004 (and again in 2014).

Ravi had an enormous capacity for friendship, with friends all over the world. Ravi preached in over 70 countries and on six continents to millions of people during his nearly 50 years of ministry. Among his closest friends were his colleagues and the board members and supporters known as Founders in his organisation RZIM. When I joined that team in 1998, we were 5 speakers internationally; now we are nearly 100 itinerant speakers. My experience of him as a leader over 22 years has been of extraordinary personal humility, and of loving and practical kindness towards those who shared his calling.

The time between his diagnosis and his death has been very short. He leaves his beloved wife, Margie, and his children and grandchildren. But he also leaves a legacy of lives changed by his preaching, countless evangelists raised up and supported through his generosity, a renewed confidence in churches across the world that the Christian faith makes sense and deserves to have a hearing in the public square, a model of courteous and robust proclamation and defence of the gospel and 28 books exploring apologetic themes. The hashtag ThankYouRavi on social media gives a glimpse of the scale of his impact but today the main accolade he will hear is "Well done my good and faithful servant!"