A sole parental responsibility order is a long term order intended to last until the child or young person is 18, and is aimed at increasing their sense of stability. (community.nsw.gov.au)
If you were never married to the child's mother or named on the birth certificate, you can apply to the court for a Parental Responsibility Order to get parental responsibility. (gov.uk)
This requires the mother's consent (and if the mother doesn't consent, you will need to go for a Parental Responsibility Order through the courts — see «E» below). (fatherhoodinstitute.org)