Police in Brixton said the man they have arrested following a fatal stabbing where a 28-year-old woman was killed trying to protect her younger sister, is known to them, but would not give any more details.
Speaking this afternoon, Detective Reynolds said young children were at the scene of both attacks, which involved "extreme violence", and officers are trying to establish whether they saw anything significant.
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Government minister Justine Greening has apparently opened up about her sexuality, as thousands took part in the London Pride parade.
Record crowds are at this year's Pride in London parade as people show their support for the LGBT community after the Orlando shooting
After a showery start to the day, parts of Northern Ireland, western Scotland and south-west England will see drier conditions.