What used to be called step parent adoptions were always approached with caution by sw appointed once that application had been made. Parental Responsibility for significant individuals, including step parents arrived when the 1989 Children Act was implemented.
Adoption within families was always something the family courts were very reluctant to approve because it changes family relationships irrevocably.
Gracesgran has summarised the law in relation to PR. I agree with your conclusion GG, Rob will be part of Henry's life until either Rob or Henry decide to end their relationship.
I'm not a fan of Rob, who could be - but in the majority of family circumstances, the law is right in making an enduring legal relationship between child and a significant adult. Many children who have no so called blood relationship with say, the father of one of their half siblings, go on to have loving and supportive relationships with that man.
Come on Helen, talk to Anna. Come on Anna, get a grip and put your personal life to one side, or calm down about it - other professional women do this. The current script writers in the Archers seem to delight in portraying the female characters as ditzy. Thank goodness for Jill.