Downing Street tried to block release of files exposing scale of cover-up . High Court Action only caved in after being threatened with Cabinet Office . Papers expose how much Establishment knew about Cyril Smith 's abuse . Margaret Thatcher was told police had probed claims he abused teenagers . She was warned that handing him knighthood risked damaging 'integrity of the honours system ' - but went ahead anyway .
Downing Street tried to block release of files exposing scale of cover-up . Cabinet Office only caved in after being threatened with High Court Action . Papers expose how much Establishment knew about Cyril Smith 's abuse . Margaret Thatcher was told police had probed claims he abused teenagers . She was warned that handing him knighthood risked damaging 'integrity of the honours system ' - but went ahead anyway .