Hi
Though the 1861 census clearly states Watson I think Maria's married surname was Weston.
1871 census RG10 351 folio 43
43 Dudley Street St Giles in the Fields
Maria Weston 40 Head Widow Tailoress Marylebone Middlesex
Mary Taylor 71 Mother Widow Dilwinn (
Dilwyn) Herefordshire
Alfred Weston 17 Son Pianoforte St James Middlesex
8th August 1852 St George, Bloomsbury
Frederick John Weston Full Age Bachelor Jeweller 156 High Holborn Richard Weston Jeweller
Maria Taylor Full Age Spinster Tailoress 156 High Holborn John Taylor Butler
Marriage by banns. Both Signed
Witnesses Frederick Henry Lees and Ann Maria Weston her mark
Deaths Mar 1854
Weston Frederick John St James 1a 252
Deaths Sep 1874
TAYLOR Mary 74 St. Giles 1b 337
1881 census RG11 327 folio 51
43 Dudley Street St Giles in the Fields
Maria Weston 49 Head Widow Tailoress (uncompl) Marylebone Middlesex
Alfred Weston 28 Son Unmarried Pianoforte maker St James Middlesex
1891 census RG12 210 folio 82
66 Neale St Giles in the Fields
Alfred Weston 37 Head Single Pianofortemaker St James Middlesex
Deaths Sep 1889
Weston Maria 56 St. Giles 1b 348
Deaths Jun 1899
Weston Alfred 46 St. Giles 1b 365
You can access the Dilwyn parish registers indexed on the IGI through Hugh Wallis' website
http://freepages.genealogy.rootsweb.ancestry.com/~hughwallis/IGIBatchNumbers/CountyHereford.htm#DThere doesn't appear to be a Mary Protherough/Prothero) baptism
Is it Alfred and Maria Weston you were searching for or an Alfred Watson?
Regards
Valda