Disabled adults and families with disabled children are challenging the legality of the Government's so-called "bedroom tax", arguing that it unlawfully discriminates against them.
Lawyers in 10 cases at London's High Court are seeking a ruling that the regulations, introduced on 1st April, "unjustifiably discriminate against housing benefit claimants who are disabled or care for disabled family members".
Outside court protesters gathered in support of the families.
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Highs rising to the mid 30s across southeast England and well above average elsewhere in the UK.