I've found James and Harriet Hutchings on the 1851 with son edwin, b tring age 18, their daughter harriett aged 11,son edward, 8 daughter caroline 6 and baby mary ann 1, wife harriett aged 40 born tring but husband james born marylebone and all the children born st martins westminster, harriett cato married james bower hutchings Q3 1838, marylebone. Harriett's marriage certificate is on ancestry and gives the couples address as 10 little ditchfield street langham westminster, her father is given as james cato weaver. I guess you've looked at that, As James Hutchings was born in alondon borough, and harriett seems to have married him there in 1838, I can't quite see a reason that James Hutchings would have been the natural father of Edwin, even though he appears to have raised edwin as his own sometime between 1838 and at least 1851 when Edwin was 18. But there is of course enough to assume that harriett was the natural mother, as her parents do not seem to have had any other children, though the name Cato does show up in tring at that time they appear to be the cousins to harriett.
Basically, Harriett must have somehow met james hutchings and i am wondering if this might be through her mother's side as there is no apparent marriage for harrietts parents in tring but possibly one in london