The phone call from British Transport Police came one night in the summer of 2005. It was about my son, the officer said. He told me that Henry had jumped on to the Tube line at Baker Street in the thick of the rush hour and my legs buckled under me.
The officer explained they had rescued him just before the train had come in and was now with the police at Goodge Street station in central London.
Why had he jumped? It was weeks before Henry told me about the voices in his head that had urged him to. He had leapt from the platform on to the track, and as he lay there waiting for the train, he imagined he was in heaven.
A psychiatrist judged him well enough to come home. I felt trapped by fear and hopelessness. I did not know how to protect my son. Nine years on, I still don't.
For Henry - my beloved only child - endures a life bereft of purpose or meaning. Nine years ago, he was diagnosed with schizophrenia. Since then his promising young life has been on hold.
For the past two months, he has been locked in a secure ward at a psychiatric hospital in South-West London because he was failing to take his medication.
Each day when I visit, Henry, now 28, paces the room like a caged animal. He still talks to the imaginary voices that bedevil him. He must be persuaded to drink, to wash, to clean his teeth.
He is thin, ashen-faced and as dependent as a baby. What breaks my heart is that it could have been prevented.
His psychosis was caused by that most pernicious of drugs, skunk cannabis, and psychiatrists have confirmed it.
Henry was a sporty, academic teenager before he started to smoke skunk.
But his development was arrested when, at 16, he started smoking cannabis, and became mentally ill. The precious years when he should have been studying for a degree, dating and embarking on adult life, have all been denied him.
His is not an isolated case: psychiatric wards are full of people like him.
This is why I was enraged by Nick Clegg backing a report that suggests the Government should legalise cannabis.
The Deputy Prime Minister has endorsed a paper from the London School of Economics that condemns the war on drugs as a costly failure and recommends experiments to legalise it.
I would first urge him to read my son’s story and consider how dangerous it would be to send out a message to children that cannabis is not harmful.
It has destroyed my son's life, contributed to the breakdown of my marriage and turned my once happy life into one of constant stress and anxiety.
Henry was a cherished and privileged child. My husband Lloyd - Henry's father - had his own household and hair products company and we had glorious homes in London and Monaco, where my work with charities brought me into contact with royalty.
Henry could not have been more loved. Happy, well-adjusted and sensitive, he was also artistic and musical. When he was nine he sang at a charity event I organised at London's Savoy Hotel.
I still remember blinking away tears of pride as an audience of the great and the good gave him a standing ovation.
Henry wrote wonderful poems, too and every Mother's Day card contained a little verse he’d written for me.
He hated being separated from us, and when Lloyd and I toured the Far East for a few weeks, and Henry, then five, stayed with his granny, he festooned the house with balloons and a 'welcome back' banner for us. I remember how he launched himself at me and squeezed me until I was breathless.
He loved acting, was a brilliant mimic, I thought one day he might be an actor.
But all those hopes are destroyed now.
I still remember the day in February 2003 when I discovered Henry, then 16, was smoking cannabis on our annual skiing holiday in Courchevel in the Alps.
An accomplished, enthusiastic skier, he was still in bed when the rest of our party was ready to go. I knocked on his door. He opened it and went back to bed.
Urging him to get up, I went into his bathroom and found a bag containing what looked like herbs. I knew it was cannabis and almost choked with anger. Shouting, 'What on earth do you think you’re doing?' I flushed it down the loo.
Lloyd was not with us - he doesn't ski - and I decided not to tell him because I knew he'd be furious. So I watched, horrified as my sporty, outdoorsy son slumped into inertia and spent most of the week asleep.
I don't know if he had other supplies - but he only roused himself from bed to ski once that week.
And during one meal there the full force of his odd behaviour struck me for the first time: he burst into manic laughter for no reason then dissolved into tears.
When we got back home - we were then living in Monaco - I hoped Henry would revert to his old self. He was among the academic high-achievers at his private day school, the International School of Monaco.
He passed his GCSEs with top grades but a new lassitude set in. He stopped playing sport. He became pallid and thin. I asked if he was still smoking, but was met with silence.
Months later, I discovered more drugs in his bedroom. I told him how disappointed I was. He just shrugged and said: 'Everyone smokes it.' I endlessly lectured him on the dangers to his health and wellbeing.
Lloyd, meanwhile, was an absent father and husband. When he wasn't building up his successful business he was out drinking and socialising with his friends. His life was remote from mine and Henry's, but on rare occasions he was home, I protected him from what was happening.
When Henry turned 18, however, he became more overtly defiant. We'd arranged to fly the family and a group of his friends to London for a party.
We stayed at Claridge's Hotel, and when Lloyd went to Henry's room where he'd been celebrating with his mates, it was clear from the manic laughter and distinctive smell they'd all been smoking cannabis.
Lloyd was beyond furious. He said he didn't recognise him as his son - Henry called his father a hypocrite because he smokes cigarettes and drinks whisky.
We flew back to Monaco: it was the start of Lloyd's alienation from Henry and the beginning of the end of my 25-year marriage which finally fractured, acrimoniously, in 2007.
I suppose I neglected Lloyd in my efforts to help our son, and the strain on our marriage was intolerable. He wanted life to run smoothly: Problems irritated him. We divorced on the grounds of his unreasonable behaviour.
Henry's behaviour became even worse when he began conversing with imaginary voices. Our GP suspected he was suffering from schizophrenia and we arranged to take him to a private psychiatric hospital in Northamptonshire, but when we were due to fly, Henry was gripped by the most horrifying psychosis.
In the end we had to charter a private jet costing £16,000.
In Northamptonshire, he was sectioned under the Mental Health Act. He had to be carried, protesting violently, to a secure unit. As he was locked up he screamed, 'Mum, Dad!' It was the worst day of my life.
When he was discharged after three months I thought the worst was over. How wrong I was. Over the next two years, we shuttled between Monaco and England, where Henry's life was punctuated by recovery and relapses. He still smoked cannabis covertly.
After just two terms at a business school in London, he gave up, and descended into a black pit of drug dependency and mental illness. By then I knew that he used skunk, a very potent version of cannabis.
I have lost count of the times he has been in and out of psychiatric hospitals in the past 11 years.
Our health insurance now refuses to pay for private treatment; so our son, now 28, is now in the care of an over-stretched, under-funded NHS.
In 2007 I saw the eminent psychiatrist Professor Sir Robin Murray at London's Maudsley Hospital and he confirmed that Henry's cannabis use had precipitated his psychosis.
Henry started smoking skunk when his brain was still developing, so the damage was especially profound.
Studies have shown the cannabis smoked in the Sixties and Seventies had a THC (Tetrahydrocannabinol: the mind-altering ingredient) content of 1 or 2 per cent. It has mostly been replaced by skunk - produced by selective breeding of cannabis plants - with an average THC content of between 16.2 per and 46 per cent.
On sensitive and still-developing young minds like my son's, its effect can be utterly devastating.
The notion that cannabis use only destabilises poor families and is 'cost-free' for the educated and prosperous is evil and dangerous nonsense. Our lives have been blighted by it.
In 2007, believing Henry would be safer out of London, I bought a house in Henley, Oxfordshire, and found a flat there for him. Months later, two thugs who dealt in drugs - whom he naively counted among his 'friends' - broke in while he slept, beat him badly, gagged him and robbed him.
It almost broke me when I found him, his eyes black, his face ballooned and bloodied, his flat ransacked.
Four years later, Henry lives in a state of terror: of the voices that plague him, of being attacked, of life.
He tells me he no longer uses skunk. But it's too late. His mental illness is now so entrenched he is incapable of independent living. Henry often tells me he wishes he was no longer alive. Then my sadness almost destroys me.
I lie awake each night consumed by anger that my son's life has been reduced to dust by this awful drug. Had he never taken it, I firmly believe he'd still be the bright, beautiful boy he once was.
I intend to move back to London now. When he is well enough to be released, he will live with me. Once again I shall be his carer as well as his mother. I see no other way forward.
Meanwhile, if I cannot hope for a cure for Henry, I can pray for remission from the abiding tragedy that is his life. All I ask for is a little normality: a modest enough hope.
Culled from Dailym