All the bodies were found within 250 yards of the mainline railway station between 11 and 19 March. Police and addicts believe that someone has been supplying 70 per cent pure heroin, twice the normal strength. It is not known whether the dealer is still selling the lethal mix on the streets.
Friends and relatives of some of the dead last week maintained that they were not addicts, but occasional users. Their lack of familiarity with heroin made it almost certain that they would die from the larger doses, doctors and local drug users suggested.
Heroin is usually adulterated with chalk or bicarbonate of soda to 35 per cent purity. High-strength heroin damages the lungs of all but the most hardened drug users.
Among those who died were a businessman from Surrey, a labourer from Scotland, a 21-year-old Irishman who had been in London for less than a month and homeless people in King's Cross bed-and-breakfast hotels.
Catherine McCallion, whose brother, Francis, 31, died on 13 March, said he had spoken last year about the dangers of owing money to criminals in King's Cross. She is pressing police to treat his death as a killing.
But the police have no evidence to back her theory. Detective Supt Mike Dixon, who is leading the combined inquiry into all seven deaths, said that while the 'extra-strength' heroin was probably responsible, it was also possible that contaminated drugs claimed the victims' lives. Police are awaiting results of chemical analysis of samples from the victims' bodies.
Commander John Townsend, of the Metropolitan police area headquarters which covers King's Cross, said he could not remember so many bodies being found in such a short period of time.
The deaths occurred while a determined police clean-up operation was under way in the red light area - which achieved national notoriety last year when Sir Allan Green, then the Director of Public Prosecutions, was cautioned for kerb-crawling.
Intensive surveillance using long-range police video cameras led to 200 dealers being arrested and charged last year. Only two of those charged were acquitted and many of the rest are now serving sentences of up to nine years.
Since the beginning of February this year, the police, in co-operation with local authorities, have launched another sweep across King's Cross. Police intelligence concentrated on 82 dealers, of whom so far 63 have been arrested, along with 66 other dealers and suppliers.
Those convicted include Italian dealers from Naples and Sardinia, who control the heroin trade, and 'yardie' suppliers from Jamaica.
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