Legal highs are so popular the only option is to "educate people who are using them" about how they can make safer choices about the drugs they take, an addiction specialist told Good Morning Britain.
Associate medical director of the CRI, David Bremner, said: "In a matter of days a new drug will be released that will have one molecule changed that then beats the law so that it is no longer illegal...all we can do is educate people who are using them on how to make safer choices."
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The Duke of Cambridge also laid a wreath to honour the victims before kick-off.
Marjorie and Michael Cawdery, both 83, are understood to have been stabbed to death in a killing their family called "incomprehensible".