Armagh man John Lennox, then a young man studying at Cambridge University, could scarcely believe his ears. There he stood in the study of a Nobel Prize winning scientist and a couple of other senior academics and he was being told to give up his faith.
Professor Lennox, now 76, a professor of mathematics at Oxford University, recounted this extraordinary conversation in Can Science Explain Everything, one of the several books he has written about what he calls the interface between science, theology and philosophy.
The scientist said to him: "Lennox, do you want a career in science?"
"Yes, sir," I replied.
"Then," he said, "in front of witnesses, tonight, you must give up this childish faith in God. If you do not, then it will cripple you intellectually and you will suffer by comparison with your peers. You simply will not make it."
Whatever the scientist's intentions his pressure on the young student 50 years ago backfired spectacularly. For John Lennox not only went on to have a glittering academic career but also became one of the foremost defenders of Christianity in a world which he sees increasingly dominated by denial of God's existence.
Speaking to me as he published his latest book - Where is God in a Coronavirus World?, a 66-page work written in just a week - he recalls that Cambridge meeting.
"I not only found it shocking, but it saddened me. His arguments were very weak, almost non-existent. That was astonishing coming from a man of such scientific eminence," he says.
"If he had been a Christian and I had been an atheist he probably would have lost his job the next day for what he did, but it seemed acceptable that he could attempt to pressure me into setting aside my Christian beliefs.
"However, the net effect was the opposite of what he intended. It put steel in me."
Indeed it did. Professor Lennox has taken part in many public debates defending his Christian beliefs against such well-known atheists as Richard Dawkins and Christopher Hitchens.
He argues: "I want to let the general public hear the truth. The world media is dominated by atheism and the Christian worldview scarcely gets a look in. I just want a level playing field. I believe atheists should be heard but the public should be able to make up its own mind having heard both views."
In his latest book he tackles the problem which many people wonder about - how can a merciful God allow disasters like the coronavirus pandemic to occur.
He accepts that in the modern world fewer and fewer people have any 'God-dimension' in their lives. In past times when disaster struck in the western world people flocked to churches and national leaders called for prayers. Today the churches are closed because of the pandemic and many ask if God is present at all.
Professor Lennox uses a quotation from CS Lewis, best known as the Belfast-born author of the Narnia Chronicles, but who also wrote extensively on Christianity after turning to religion from atheism in middle age, to make a point: "God whispers to us in our pleasures, speaks in our conscience but shouts in our pains: it is His megaphone to rouse a deaf world".
He adds: "Like me and my wife, many people are locked down at the moment and that gives us more time to think about big questions like why do we have pandemics or wars or famines. These questions wake us up to the fact that we are mortal and vulnerable.
"At these times the God question is never far away. It is like a megaphone shouting to us - think about your mortality as a human being; is there more to life than the materialism that we have got used to?"
He defends God against the charges made by some that pandemics like coronavirus are a punishment for sins committed, drawing on Biblical authority to back his case, but admits that Jesus did warn people to repent of their sins.
"It is not legitimate to see this as God's judgement on massive sinning against Him. But Jesus did say that unless we repent we will perish. This should wake us up to the fact we have neglected Him. If catastrophe reminds us of that fact then it does some good amidst the harm."
He adds: "It is very dangerous to claim the moral high ground claiming we know what God is doing."
At these times the God question is never far away. It is like a megaphone shouting to us - think about your mortality as a human being
Professor Lennox as a young man at Cambridge struck up a friendship with CS Lewis who he describes as a "tremendous mentor to me" and as one who helped him reject the demands of the scientist who wanted him to give up his belief in God.
"I have not known what it was like to be an atheist as an adult like Lewis who only became a Christian in later life. However his understanding of the Christian message and his articulation of it was tremendous."
Professor Lennox's faith was grounded in his Armagh home. His father owned a large general store in the city, employing around 30/40 people.
"My parents were Christian and they made a wonderful impression on me. They were Christian without being sectarian. In those days there was a lot of sectarianism in society. My father employed Catholics and Protestants - it may have cost him some trade - and when I asked him why he told me that all people were made in the image of God. That was a hugely important message to me.
"My parents did not push Christianity down my throat and, indeed, encouraged me to understand other worldviews. I owe them a tremendous debt."
Not only is his Christian faith well grounded but it is also steadfast.
In his latest book he recalls how some years ago he was rushed to hospital with severe chest pains. He was told to say goodbye to his wife Sally. He is in no doubt that the swift medical intervention prevented him having a massive heart attack which would probably have killed him.
Around the same time his sister's 22-year-old daughter, who had just very recently been married, died from a brain tumour.
Did that shake his faith? "The more important question is did it shake my sister's faith or the girl's husband's faith? The answer is no. At this stage of my life I have sorted out certain things in the sense that I know I will die one day - it could even be in this pandemic - but what preparations have I made for death and its aftermath?
"People often ask me if I doubt. I spent my entire life making my faith in God open to questioning including hostile questioning. That is what has led me to hold the convictions I have at the moment. I have been doing that for over 50 years. Of course problems of suffering and evil are the hardest questions any of us face.
"Faith simply means trust. But what do we have faith in? This is not some sort of Santa Claus belief. Faith in Christ and God is evidence based trust, the kind of thing involved in any good human relationship. Everyone believes in certain things and sensible people believe them on the basis of evidence. My hope for the future depends on Jesus' resurrection for which I believe there is historical evidence."
This time of the year has particular resonance for him as it does for all Christians. His belief in the resurrection and therefore a life after death is what he believes sets Christianity apart from other faiths and poses a question which atheism cannot answer. Christianity offers an ultimate justice. People may have escaped justice or been denied justice in life but Christianity has a final arbiter in God.
So what makes this father-of-three grown up children and grandfather-of-ten want to continue with his Christian crusade? "I find that the Christian message of forgiveness and peace in God through Christ is a message which I cannot keep to myself. Jesus told his followers to go out into the world and spread this message and I am trying to do what he said."
He has an ally close to home, his niece Kristyn Getty. She and husband Keith are acclaimed modern hymn composers who spend their time divided between Northern Ireland and Nashville, Tennessee. Professor Lennox is proud of their work - "they write wonderful hymns and are connecting through their music with a generation of people I would never reach" - and also from the fact that he played a part in their success, having introduced them to each other.
But then Professor Lennox is not just some dusty academic with an intense interest in maths and religion. His hobbies include amateur astronomy, birdwatching and languages - he speaks English, Russian, French and German - and walking.
Where is God in a Coronavirus World? by Professor John Lennox is published by The Good Book Company, price £2.54