By Anna Holligan
BBC World Service
'Khat' is a popular stimulant chewed across east Africa. Now it is crossing cultural divides and becoming a drug of choice for an increasing number of young people in the UK.
The khat plant,
, has been chewed by east Africans for hundreds of years and plays a large part in the social lives of both men and women.
It is banned across America, Canada and most of Europe, but remains legal in Britain.
Khat user Steve [not his real name] is a philosophy student. He is one of an increasing number of students who are taking up the habit.
Steve, who is 22, comes from a good middle-class family and in a slightly apologetic tone he tells me he was drawn to the leaves because they looked harmless.
"They looked really natural, not like a normal drug and they were all wrapped up in this really shiny banana leaf."
Chewing khat according to those who do it, gives them a mellow high. Some describe it as a cross between cannabis and cocaine.
"You're really alert," says Steve, "but at the same time you have a bit of the feeling you have on cannabis... not hallucinations but going that sort of way."
In Somalia, khat is popular among taxi drivers and farm workers - people who have to stay alert while the rest of us are tucked up in bed.
In the UK, some students are using it for the same reasons, saying it helps them stay up all night studying.
It is relatively easy to get, and it's cheap too - your average bundle costs about £3 ($.4.20).
When I went in search of some for this piece, I was pointed in the direction of an Ethiopian butchers in north London.
Khat's appeal is spreading beyond the Somali community
They had sold out, but assured me they were expecting a fresh batch to be delivered in a couple of days.
The woman behind the counter suggested I try down the road.
Next stop and sure enough there it was, nestled innocently between the cucumbers and courgettes.
"Aren't you worried about selling it," I ask.
"No, why should I be?" The store owner asks, with a slightly bemused look on his face.
"Its legal, we pay taxes and people want to buy it, so I sell it."
But there growing concern that khat houses are trying to appeal more to younger users.
And that according to Asha, a teenager we meet at a community centre in east London, is setting a dangerous precedent.
"I see so many kids who...start because they just want to try it, but then they end up going there 24/7," he says.
"I know [people who] have ended up dropping out of college because they've been up chewing all night and can't get out of bed. Plus you get people selling other harder drugs in there."
But it's not just the impact on academic results critics are concerned about.
Heavy use can lead to insomnia, high blood pressure, heart problems and impotence
Longer-term risk of developing mouth cancers
Can create feelings of anxiety and aggression, and cause paranoid and psychotic reactions
Can make pre-existing mental health problems worse
Psychiatrist Dr Eleni Palezido reckons that khat can be a catalyst for mental health problems.
"When you stop taking khat all the dopamine (a chemical associated with feelings of pleasure in the brain) leaves your system, so people get depressed, they can get paranoid, hear voices and it can lead to a full blown psychotic state."
Cathinone and cathine are the main ingredients of the plant. Both are class C drugs in the UK, but the plant khat itself is not classified and can be bought openly in shops.
Cathinone is almost identical to amphetamines and it is this that creates a high. It's known to cause mental health problems like psychosis and depression.
And that is one of the reasons why some in the medical profession, like Dr Palezido, are worried.
"Young people have no idea about the dangers, they think because it's legal it must be ok, but it's not."
So far, the Government has been reluctant to introduce a ban on khat.
KHAT: LEGAL STATUS
Banned in the US and Canada
Banned in many European countries - Norway, Sweden, Denmark, Finland, Ireland, France, Germany, Switzerland - but not the UK
Although, the Home Office told us they were "continuing to monitor the situation."
Around seven tonnes of khat arrives at Heathrow every week from Ethiopia, Kenya and Yemen.
The fact that it is legal here has meant the UK has become something of an international hub for illicit trade in khat to other countries where it is banned.
There are no official figures on how many young British people are using khat, but Asha reckons the politicians should act now before it's too late.
"The government should be doing something about it. They think it's just Somalis who are doing it but it's not....everyone's now getting involved."