If I am on the right track then Thomas Brown (of 1st Berkshire regiment) died sometime between 1907 and 1911.
The next step would be to get the marriage certificate to get more information about Thomas. This might make it easier to find a death for him.
Marriage Jan-Mar 1903 Reading Berkshire - Annie Ruth Raven to Thomas Brown
The mother appears to have been
Annie Ruth Raven born 1882 in Bradfield Berkshire (father William Raven, mother Annie Brunsden)
Birth Registration (surname mis-spelled)
RABEN, ANNIE RUTH Mother - BRUNSDEN
GRO Reference: 1882 M Quarter in BRADFIELD Volume 02C Page 351
I would look for her in the 1921 census with the surname Brown, or look for possible marriages for her after 1911