Statute is not to alter existing common law

Dear Mike, I studied entire book and kit however one confusion is not going out of my mind. One thing is Common law which was developed following Norman conquest. Then developed Equity. Then using Common law and Equity principles the Statute is developed. However, in these times, judges give the decision inline with the Statue. Not referring Common Law and Equity (right? or may be i am wrong. Here i want to clear my mind). And if the Common Law and Equity is being referred in these times as well then why there was a need of statute. Moreover, as mentioned in the title that "Statue is not to alter existing common law", then what would happen if there would be a conflict between these two. Judges would refer to what Mike you are really helpful all the time. I know i may be asking bullshit but this is what my mind is not picking up.