the director of public prosecutions who let off lord janner over alleged child sex abuse started her career at a legal chambers when the disgraced labour peer was a top qc there .
alison saunders , 54 , sparked outrage last week when she decided the 86-year-old should not face a string of charges of paedophilia against nine children because he has dementia .
today , newly-released documents revealed damning evidence that abuse was covered up by police and social workers for more than 20 years .