The co-defendant in the the Tulisa Contostavlos trial has also walked free after the judge decided the case against him could not proceed.
Rapper Michael Coombs, whose stage name is Mike GLC, had pleaded guilty before the trial to supplying half a gram of cocaine to undercover reporter Mazher Mahmood.
On hearing the decision the 36-year-old reportedly wept and hugged his defence barrister, Jeremy Dein QC.
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Tony Davies was the first civilian to reach Pc Palmer after he was stabbed during the Westminster attack.
Defiant Londoners put on a show of solidarity for the victims of the Westminster terror attack at a vigil in their honour.
Weather set to improve with plenty of sunshine by Saturday