Boris Johnson was booed and heckled by an audience made up of hundreds of campaigners last night.
The Mayor was confronted about the downgrading of services at Lewisham Hospital at People's Question Time in Catford.
Ronke Phillips reports:
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The man was taken early this morning to a south London police station where he remains in custody.
Officers arrested a 15-year-old boy in Stratford on Saturday night on suspicion of grievous bodily harm.
Six people were injured after they were hit with the substance during an "altercation" between two groups at a shopping in east London.