Strong , if you can prove to the High Court - Family Division that the mum is liable of these claims.
However the child may be required to give evidence in court or a video taped interview (but don't quote me on this, it was 4 years ago when i studied family courts, and this may have changed.)
Research the Children Act 1989, read all you can and pay particular attention to sections 1 - 7 and 10.
Also research the Child Abduction and Custody Act 1985.
Consult a family specialized solicitor to get an in depth look at this matter.
If you need more post back or message me. But dont keep me in the dark.
Cheers