You can’t be around Rick Warren for long without getting an all-enveloping bear hug. I’ve had a couple already, and most of the people we’ve passed in the hotel lobby are getting his trademark ‘hug-a-pastor’ treatment too.

Warren (Pastor Rick to everyone who knows him) is an emotionally generous sort of person. Gregarious yet intensely personal, once we begin to talk he holds nothing back. He laughs frequently, talks passionately, sometimes cries – often all within the space of a few minutes.

I had wondered how to sensitively broach the subject that I knew we must address – the suicide of Matthew, the youngest of his and Kay’s three children, one year ago. Their son’s battle with depression had been something only family friends knew about, but as his tragic death made headlines around the world, the Warrens’ personal grief would be lived out in the public spotlight. In the end, my questions took a back seat as Warren simply talked and talked, pouring out his heart as he recounted a year that has had a more profound effect upon him than any other.

For more than three decades Warren has been an incredibly influential Christian leader in the USA. Saddleback Church, planted from scratch by a 26-year-old Warren and his wife Kay in 1980, quickly grew in size as the fledgling pastor’s down-to-earth sermons drew increasingly large crowds. Today more than 20,000 people attend weekend services at the multi-site church in Orange County, California.

Then, after writing a best-selling book on church growth, The Purpose Driven Church (Zondervan), Warren went on to write the best-selling Christian book. Ever. The Purpose Driven Life (Zondervan) has sold more than 30 million copies since its publication in 2002 and is the second most translated book in the world after the Bible. After its extraordinary success, Warren gave up his pastor’s salary and used more than 90% of the earnings to launch a number of global charitable initiatives, including the ambitious PEACE Plan.

When we meet, Warren has just finished speaking at the HTB Leadership Conference, for which he tells me that he’s not taking any payment – he considers it a gift to share his experience with leaders around the world.

Meanwhile, his global influence is hard to overestimate, not least because Warren somehow manages to cross political and theological boundaries. When Obama was inaugurated, the new President chose Warren to deliver the prayers, yet political conservatives see him as a compatriot too. He has appeared on Oprah Winfrey’s TV show to deliver motivational life coaching, and has also preached to conservative evangelicals at John Piper’s Desiring God conference.

Like any public figure, Warren has his detractors, from liberals who decry his consistent stand against gay marriage to theological hardliners who believe his motivational brand of seeker-sensitive Christianity sells the gospel short. What neither side can deny is his enormous popularity in the States and worldwide appeal. When he was finally ready to talk about Matthew, millions watched Piers Morgan interview him and Kay in what the TV host described as ‘the most moving interview’ he had ever conducted.

A year on from the tragedy, he and Kay have begun to talk even more openly about their experience. ‘There is no growth without change, and there is no change without loss,’ he reflects on his journey through the stages of grief.

Their story has already had an enormous impact. Suddenly the couple have earned a voice with a new audience – the millions of other parents, siblings, friends and families affected by mental illness. Maybe I shouldn’t be surprised that the man who wrote the world’s best-selling book on purpose is already seeing a greater design being fashioned from the rubble of tragedy.

Take us back to Easter last year...

The day that I prayed would never happen, the day that I figured might happen, happened five days after Easter last year.

Since Matthew was a baby, we’ve known that someday we would become spokespeople about mental illness. It was hard enough being my son, much less to struggle with mental illness; it was his story to tell, so to protect his dignity we kind of kept it quiet.

After his death I said we wouldn’t do any interviews for six months – we didn’t even know what we were feeling, we were just grieving parents.

Eventually, I started sharing my feelings on social media and I realised that people were coming out of the woodwork and saying, ‘That’s me, that’s my problem, or my brother’s problem.’ The floodgates opened. I’m not exaggerating; maybe 10,000 people have written or connected in some way saying: ‘I lost a friend through mental illness.’ Everybody knows somebody.

Can you describe what happened that day?

That week was what I call ‘my battle for hope’. Last Easter was the 33rd birthday of Saddleback and we had more then 50,000 in attendance – it was a big day for us. Many people came to Christ and I preached on the hope of resurrection. At the end of the message I said, ‘The more people I love that are in heaven, then heaven becomes closer and more real to me. My mum is there, my dad is there, my brother is there, and I have a lot of friends there.’ I didn’t know that five days later my youngest son would be there too.

Matthew had been over the night before, all perfectly normal. We often watched TV together and laughed. He was a brilliant, really brilliant kid, with a tender heart but a tortured mind.

The night that Matthew died, we were standing outside the front of his house with the doors locked. We were waiting for the police to come and break down the door and we feared the inevitable. We were standing, Kay and I, holding each other, sobbing. Kay was wearing a necklace that had two words on it: ‘Choose Joy’. She said: ‘Choose joy.’ I looked at her and thought, ‘Are you kidding me? How do you choose joy when your son on the other side of that wall has probably just taken his life?’ But that’s faith.

Who has been there for you through this?

My small group was the stability for me in this last year. When Matthew died, within 30 minutes they were there on that sidewalk with us, hugging us, and just being with us. The deeper the pain, the fewer words needed.

That night they came and spent the night at our house. We didn’t have beds for them; they just slept on the couch and in the kitchen, saying, ‘We’re not leaving you alone.’ The next day I sent a letter to my church saying, ‘I’ve been your pastor for 33 years, I need you now, I need you to pastor me for this time.’

I’ve done maybe 1,000 funerals in my time as pastor. I've been at the bedside when a lot of people have breathed their last breath. The most difficult is the death of a child, without a doubt. You’re not supposed to outlast your children. Suicides are the hardest funerals to do...and then I'm doing a child’s funeral, my own child’s suicide.

There were people on the Internet celebrating my son’s death, writing all kinds of vile things, and saying, ‘May he burn in hell.’ Lots of people were actually celebrating and rejoicing, and armchair therapists were determining why he’d taken his life. That was pretty brutal.

It must have compounded the shock and the grief. How did you cope with it?

As a public figure there is never a day of your life that you are not criticised. You have to live for an audience of one; you can’t worry about what other people think. The fact is they simply don’t know. Jesus was perfect, and yet he was criticised, attacked and crucified. A lot of people think, ‘If I could just be perfect, then everybody would like me.’ No they won’t – even Jesus was hated.

You have to learn to have a thick skin.

A thick skin, and a tender heart.

But the past year must also have changed you?

When Matthew died, I took a four month grief sabbatical. I did not preach, I did not teach, so I spent eight hours a day alone with Jesus. I’m not the same man I used to be. I’ve got the same personality, the same flaws, but I’m just not the same guy I was. You can’t spend four months alone in reflection, in the Bible, with scripture and with Jesus and it not change you, deepen you and sensitise you to the pain of other people.

When things happen to you, they become part of your life message. It doesn’t replace my life message, it just adds to the mosaic. It’s another piece that’s been added.

This all came in the midst of plans to launch a Saddleback church plant in London. Is that still going ahead?

We’re hoping to start Saddleback London at some point. Ten years ago we launched the PEACE Plan as a way of fulfilling the great commission. PEACE stands for: Plant churches that promote reconciliation, Equip ethical leaders, Assist the poor, Care for the sick and Educate the next generation.

Every ten years we set a goal for our church. In 2010 our goal was: why don’t we be the first church in 2,000 years to literally go to every nation?

The whole idea of Saddleback expanding to what we call ‘strategic global cities’, like London, is to establish base camps to resource churches that will go to other places around the world in mission. Our goal of going into each city is not to be the biggest church; it’s to be the most resourceful church. I’ve trained more than 400,000 pastors in 164 countries. A lot of them had to come to the States. But they said that if we put a training hub in Berlin, Moscow, Johannesburg, Tokyo, then they wouldn’t all have to come to the US.

Looking back, is it possible to begin to see purpose in your pain?

I saw it from day one. In fact, we can’t handle pain unless we understand there is a purpose. The gospel doesn’t offer painless life on this earth, but it does offer us meaning, which makes pain bearable. The first stage was shock, which is a human emotion. Sometimes I’d be sitting at home at night, expecting him to walk in through the door and watch TV with us, as he often did. Then it went to sorrow, which is a godly emotion. The Bible says, ‘Jesus wept.’ The only reason you are able to grieve is because God grieves. The Bible makes it very clear; we were made in his image.

The third phase is what I call struggle. All the ‘why’ questions. The biggest one for me is, ‘Why didn’t you answer the prayer I prayed every day for 27 years?’ The prayer I prayed more than any other prayer went unanswered. But explanations never comfort. What you need in tragedy is not an explanation, you need the presence of God.

Then you come to the stage of surrender. Surrender is when you say I’d rather live and walk with God and have my questions unanswered than have all my questions answered and not walk with God.

Has this shaken your faith in any way then?

Not at all. Piers Morgan asked (we finally did one interview, and we chose CNN because we knew it would go worldwide) whether I ever doubted God or his existence. I said, ‘No, I never did, but I doubted his wisdom.’

My kids have never doubted that they had a father and that I loved them. But they’ve often doubted my wisdom. I remember when Matthew was 17, he came to me and said, ‘Dad, it’s really obvious I’m not going to be healed of this mental illness. We’ve gone to the best doctors in the nation, I’ve taken the best medicine, got the best therapy, we’ve had prayer, lawyers, intercessors, everything you can imagine and nothing has worked. Why can’t I just die and go to heaven?’ What do you say to that as a father? He was a kid who had been in pain since he was born.

I said, ‘Matthew, you may want to give up, but I cannot. As your father I have to believe, always, that there may be an answer out there somewhere.’ He made it another ten years.

What are your abiding memories of Matthew?

I think he is probably one of the bravest people I’ve ever met. He could walk into a room at a party and instantly know who was in the most pain, as he was also in pain. He’d make a beeline for that person and spend the rest of the evening encouraging them; he would have made a great Christian counsellor.

When Matthew died I received 5,000 letters of condolence from around the world. Everyone wrote from rock stars and prime ministers to presidents. But the ones that meant the most to me weren’t from the VIPs; they were the letters from people that Matthew had led to faith in Christ. They said, ‘I’m going to be in heaven because your son brought me to Jesus.’ I wrote in my journal: ‘In God’s garden of grace, even broken trees bear fruit.’ And we are all broken…God only uses broken people.

You can hear the full interview with Rick Warren on The Profile, Saturday 12th July, 4pm on Premier Christian Radio.