Agree with Harry about the longterm malign effect of MacPherson, (and by extension, Scarman,) but I'd also add another case: Soham.
Ian Huntley was a failure of what we would today call safegaurding, and marks the origins of what we would now call safeguarding. The police checks of the day failed because they were insufficiently rigourous. The proper response should have been to tighten them up, but the case was marked with tabloid hysteria. It came at the height of the Posh & Becks madness, and had those girls been wearing Cambridge United shirts, we would have hardly seen the picture. But it was Man Utd shirts, and the call went up, not for tighter regulations but perfect regulations that would ensure with 100% certainty that this could never happen again.
The response of a confident government with a large majority ought to have been mature, but this was the time when Blair was asking around for "Eye-catching initiaties with bite I personally can be associated with," and so we have the vast expensive empire of DBS, and the spread of the climate of fear across all recruitment processes over tiny little things in people's distant pasts that no one ever worried about before.
DBS is a self-serving monster that is easy to fool if you have malign intent. In particular, the part about former addresses which relies on the honesty of the applicant. It is nothing to do with protecting vulnerable groups and everything to do with organisations protecting their own backs.