Looking for Mortimer of England

Mary Ann Mortimer b circa 1797, married Thomas Mallam in 1820 at Bloomsbury St George. Ann Mortimer signed as witness to the marriage.

Separated from her huband by 1829, Mary Ann was convicted & transported to Van Diemans Land in 1830, died 1858 at Westbury, Tasmania.

Parents are unknown & birthplace is unknown but I presume Middlesex. Possibly her mother was Ann or Elizabeth, as this is what she called her 1st child born in Tasmania, Australia whilst she was alone.

Does anyone know anything further about her please?