I'd been back at work four months when, in April 1999, I had to fly to New York for four days for business. Going into the office and leaving my baby had been painful enough. Flying to a different continent pushed me over the edge.
I didn't know what was happening. My heart was thumping. I was too anxious to sleep or eat. Everyone's voices were shrill and I couldn't connect with what they were saying.
On the final day I was in the lobby of New York's Four Seasons hotel. A car was waiting to take me to the airport.
Instead, I stumbled to the reception desk and asked the lady there to book me a one-way ticket to California. It was completely irrational. But I just wanted to escape as far as possible from my life. Her face registered such shock, it brought me back to reality for a second. I knew then I was terribly ill and that I couldn't run away - I had to go back to London and get urgent medical help.
And that's how I found myself in the psychiatric ward of London's private Cromwell Hospital. I was diagnosed with post-natal depression - the term given to clinical depression that starts within a year of a woman giving birth - but it was more than that.
Ian was advised by the psychiatrist to tell the office I was sick, and not give the reason in case it damaged my career.
I was in hospital for nine weeks. I was so heavily medicated I remember very little of that time. But I will never forget the terrible feelings of guilt and worthlessness. To avoid stress, I was banned from having any contact with work. But that made me feel even more useless.
When I was finally allowed home I was still so heavily medicated I couldn't even concentrate long enough to read a sentence. Ian was extraordinary. He was convinced that one day I would be myself again.
But it was a long journey. I returned to work, on a three-day week, just before Oscar's first birthday. It was a terrible mistake. Everyone treated me with kid gloves - they either knew or had guessed what had happened. I felt humiliated and was convinced everyone was judging me. Most of all, I missed Oscar desperately. When I finally resigned, I felt only relief.
No one was ever able to explain why I'd had a breakdown. I was on medication for two years. I went through therapy and read endless books on depression. Now I'm convinced the answer is actually very simple. Depression is often the reaction to needs not being met. I had a basic need to be with my baby and I totally ignored this very primitive instinct.
We sold our home in London and our country house in Shropshire and, in 2002, moved to Sussex. I was determined I was never going to leave Oscar again.
I've managed to re-invent my career and become a novelist but my son is my real source of joy, and it's total bliss to be able to be a hands-on mother to him. He's passionate about reading and sport. I'm there cheering him on from the sidelines at every match.
Even so, I was still dogged by a sense of failure until that evening at the West London restaurant almost two years ago when I had to face my former colleagues. I felt I had let everyone down - myself included.
I was convinced that everyone inside would remember me only as the woman who crashed and burned. But one of the staff flung the door open and I was forced in. There were cheers and hugs and, as the evening unfolded, I realised how blessed I am.
Too many of those high-flying men had lost their wives, their jobs and their health. I left my career with the most important thing intact - my family.
• Aifric Campbell's novel, The Loss Adjustor, is published by Serpent's Tail at £10.99.