A coroner has said that heroin is likely to have played a part in the death of Peaches Geldof. But how many people use the drug?
In the 1950s, heroin use in the UK was almost unheard of.
The number of users was in the dozens, according to Harry Shapiro from Drugscope. Many of them were middle-class, he says, and some were doctors.
There was a rise in the number of users during the 1960s, he adds, but even by the start of the 1970s there was not a clear sign of how big the problem would become, as there were only about 1,000 registered users.
It was towards the start of the 1980s that the use of the drug started to become more prevalent.
"At that point our heroin problem really takes off big time," says Mr Shapiro.
The period saw an increase in the amount of smokable heroin being imported from the Middle East, he continues, and removed the taboo of needle use.
With the UK in the grip of economic problems and high unemployment, the problem of heroin use became more noticeable in society.
The rise of the issue can be seen in the popular culture and news coverage of the time. Grange Hill - the school-based children's drama - tackled the issue when Zammo Maguire became addicted to the drug. Boy George was a chart star and heroin addict at the same time. And Olivia Channon - the daughter of Trade and Industry Secretary Paul Channon - died from an overdose at the age of 22 in 1986.
Over the rest of the decade, use of heroin continued to grow and in the 1990s its base expanded - according to Dr Tim Millar from the University of Manchester - spreading from urban centres to surrounding towns and villages.
Estimates suggest that it was towards the end of the 1990s that heroin use in the UK peaked - with around 350,000 users, according to Mr Shapiro.
Exact figures, however, are difficult to measure.
According to 2012/13 Crime Survey for England and Wales, an estimated 0.6% of the population aged between 16 and 59 - around 200,000 people - have tried heroin at some point in their life.
The same survey suggested that 0.1% of the population (around 33,000 people) had used the drug within the past year - considerably lower than cocaine (2.2%) and cannabis (6.4%).
The rate of use has remained fairly constant. The survey suggests the percentage of the population using heroin has not changed since 2001/2.
The equivalent survey in Scotland, put the figure for usage within the previous 12 months at 0.5% (around 22,000 people) in 2012, while the figure for Northern Ireland is due to be published next month (the last figure, for 2008/9, was 0.1%, or around 1,100 people) .
But the survey is an estimate based on household questionnaires.
As Dr Gordon Hay, an expert from The University of Liverpool, points out, heroin users often remove themselves from society - making it unlikely they will take part in answering such questions.
That means the survey often misses people out - and can also be unrepresentative of the figures of usage among those who are homeless or in prison, adds Dr Millar.
When other studies are considered, the problem seems to be significantly bigger.
According to Public Health England (PHE) figures, there were around 262,000 users of drugs classified as opiates in England in 2010/11. The majority of them were heroin users, according to Dr Millar, who helps collate the figures.
PHE bases its figures on what Dr Millar calls a "more sophisticated statistical approach" - including analysis of treatment and criminal records.
According to figures collated for Scotland in 2004, it was believed the number of opiate users among people aged 15-54 was 55,800 in 2000 and 51,582 in 2003.
To give an international comparison, it is estimated there are around 500,000 heroin addicts in the US from a population of around 314 million.
In Afghanistan - where opium cultivation is a serious problem - it is estimated one million people are addicts, from a population of around 35 million.
Fewer young users
There has also been a change in the groups taking heroin.
During the 1980s, it was young people who experimented with the drug, Dr Miller says.
But now it seems fewer youngsters are starting to use heroin.
The National Treatment Agency - PHE's predecessor - said last year the number of people under 35 using heroin and crack cocaine was "plummeting", with an estimated 41,508 15 to 24-year-olds using the drugs.
This could be the result of a number of causes: education, treatment and even the increasing trend of party drugs like cocaine and ecstasy.
But at the same time, the NTA warned the proportion of those aged over 35 being treated for drug use is increasing, with an estimated 113,466 users in the 25-34 bracket. For 35 to 64-year-olds, the estimate was 143,778.
Paul Hayes, chief executive of the NTA, said at the time: "The drug population is ageing. We have very few people in their teens and 20s using heroin and crack, and more in treatment in their 40s and 50s who are frailer, iller and more difficult to turn around in the system."
Dr Millar also says that the number of people stopping their heroin use is larger than the numbers starting to take the drug. If that pattern continues, it is likely the numbers will continue to drop.