High court consent decree 1985

Consent decree got from the court by seller executors and buyer occupants in possession in 1985. Decree was placed before the stamp duty registration in the year 1998 when executors expired only by the buyer. Can we considered this registration authentic in the legal language? Can we challenged this consent decree null & voit? Thanks/regards. Your expert opinion required on your LCI Forum and my email address aeshroff@gmail.com