Detectives in Greenwich have arrested a 53-year-old woman in Deptford in connection with an incident in Eltham High Street on Thursday 13th September where a baby was given an unknown substance.
She remains in custody at a south London police station.
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A former health and safety chief said building regulations are confusing and the profession suffers from competence issues.
The tiny card, which is 15 microns by 20 microns, even includes an intricate inscription of a snowman and seasonal messages.
Police say they have traced four drivers who are thought to have hit the woman, and added that a fifth vehicle may also have been involved.