Housing benefit will no longer cover the housing costs of private renting, workless families with 3 or more children anywhere in London.
For low-income single adults without children, a third of London's boroughs (34%) are unaffordable under the welfare reforms.
Demand for the cheapest properties means that even 13 of London's 19 outer boroughs are unaffordable for families reliant on housing benefit.
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Temperatures are expected to get warmer throughout the day with highs of 21C expected to make today the hottest Halloween on record.
But Tower Hill Underground station just a few hundred yards away will be shut because of engineering work on the District Line.