Campbell set about a group of toddlers with a 2ft machete because he thought they were "little devils". He heard their voices taunting him, calling him "nigger". Christopher Clunis, known to be mentally ill, also heard voices taunting him with racist jibes. He stabbed Jonathan Zito to death in an underground station.
Last year, Stephen Laudat, a known paranoid schizophrenic released into the community without any medication, stabbed Bryan Bennett 82 times because he believed that he was was Ronnie Kray. An independent inquiry into the killing concluded that racial prejudice and poor co-operation between doctors and social workers helped turn Laudat, 26, into a violent killer.
All three were black men, tormented by real or imagined racism. In each case the authorities, through ignorance or prejudice, failed to give them appropriate treatment, and innocent people were hurt or killed.
Since the 1970s studies have shown that a disproportionate number of black people, men particularly, undergo treatment for mental illness: schizophrenia and psychosis rather than depression. Research by Professor Glynn Harrison, of the University of Nottingham, revealed last year that immigrants with Afro-Caribbean backgrounds are five times more likely to develop schizophrenia than other population groups, more than other immigrant groups, and more than if they had stayed in the Caribbean.
Before the Government began closing our mental hospitals, those black immigrants admitted to them were five times more likely to be diagnosed as schizophrenic than UK-born first admissions. People born in Britain to Afro-Caribbean parents were three times as likely to be admitted to hospital as diagnosed schizophrenics as other black people and 12 times more likely than white Britons.
So, do Afro-Caribbeans living in Britain have a genetic predisposition to mental illness or is there some other explanation? A number of theories have emerged in recent years.
First, there is the role of the police. Many more Afro-Caribbeans have been "sectioned" (locked up) under Section 136 of the Mental Health Act as a result of contact with the police than after referral by doctors. In 1983 Mind, the mental health charity, completed a three-year study which found a disproportionate number of Afro-Caribbeans among police referrals and criticised the police for "inherent racism".
Institutional racism in British society was suggested as a contributory factor by the Government's Chief Medical Officer, Kenneth Calman, in 1992 when he carried out a study that found schizophrenia was three to six times more common among Afro-Caribbeans living in England than among those in Jamaica. His subsequent report suggested that the mental illness may be triggered by stress caused by racism and unemployment.
Finally, there are suggestions that black people have been misdiagnosed as mentally ill because their behaviour is radically different to their white counterparts. Explosive displays of extreme emotion such as anger or distress, common to black culture but alien to white doctors and social workers, lead to confused signals.
For whatever reason, black people are disproportionately likely to come into the care of the mental health services. Once there, like Stephen Laudat and Christopher Clunis, they are unlikely to be well served.
Research into psychiatric treatment suggests that black people have been given harsher medication than equivalent white groups. In the mid-1980s, it was found that Afro-Caribbeans were more likely to receive powerful drug treatment in secure facilities, and they were more likely to be given electroconvulsive therapy (ECT).
Orville Blackwood, 31, died in Broadmoor Hospital in 1991 after he was injected with tranquillisers. An inquiry report by Professor Herschel Prins, of the Midlands Centre for Criminology and Criminal Justice at Loughborough University, concluded: "There is racism in Broadmoor Hospital. It is not on the whole deliberate or necessarily conscious, although there was some evidence of direct racism.'' The report notes that when the inquiry team first visited Broadmoor Hospital two months after Blackwood's death, his "name on the patients' list of the occupational therapy office wall was crossed through with `RIP' annotated against it, and nearby a copy of a magazine cartoon of Orville the Duck was still visible''.
Dr Veena Soni Raleigh, author of the Mental Health Foundation's most recent report (published last year), says: "There is overwhelming evidence that African-Caribbean people are subject to greater coercive control by both the psychiatric and criminal justice systems. It is widely believed that community and primary health-care services often fail to provide African-Caribbean people with the preventive and supportive care needed at an early stage to prevent the development of a crisis in mental health."
The common thread that runs through disproportionate sectioning by the police, misdiagnosis by health workers, and mistreatment of black mental patients is racism. Not the risible spectacle of skinheads marching through London's East End, but the hard, unspeakable reality that in Britain a black life is worth less than that of others, or is even worthless.
Blacks exercise little economic power, and almost no political power. They are disproportionately unemployed, low paid, from fragmented families. The Labour Party takes the black vote for granted, the Tories and Liberals can't be bothered to chase it.
Consequently, who cares if blacks are given inappropriate medication, mistreated or abused in care? Why worry about sectioning them, locking them up, whether they are "nutters" or not?
My life could not have been more different from Horrett Campbell's: I come from a stable, nurturing home, and had a better education than many of my peers. I have a career, a wonderful wife, a beautiful daughter, good friends. And yet a thousand tiny sleights, daily reminders of my "worthless" status, gnaw at me until I seethe with silent, suppressed rage.
Should I be troubled by women clutching their handbags as I pass by, bar staff ignoring me until white people have been served, receptionists assuming I am a delivery boy, patronising fools telling me, "You should be working for the Guardian, man"? Or am I being too sensitive, are these things really happening? Where does awareness end and paranoia begin? Without the comforts and privileges I enjoy, would I even now be in a secure mental home? Or would I be heading for a local school, clutching a machete, like Horrett Campbell?