Other Events and Attributes:

• Census: 1871, Warren Cottage, Longworth, Berkshire, England
• Census: 1881, Stoneyard, Longworth, Berkshire, England
• Occupation: 1881, Longworth, Berkshire, England; Teacher
• Address: 3 Jul 1889, 68 James Street, Cowley, Oxfordshire, England; Address given on marriage certificate
• Census: 2 Apr 1911, 21 Magdalen Road, Cowley, Oxfordshire, England
• Occupation: 2 Apr 1911, 21 Magdalen Road, Cowley, Oxfordshire, England; Private Means

Notes:

According to all the research that we have carried so far, Clara never married.
She appears on the 1871 and 1881 England Censuses as a single woman.  Then, on the 1911 Census something strange happens. - her status changes, to Widow.
Her entry is on the second row, written in a different hand and with a very different pen.  It's almost as if the older woman, the Head of the Household, completed her details and then gave it to the younger woman with a weary word, "Go on my dear, you complete the rest of it, my eyes aren't up to it in this light."  And, as if to confirm that idea, the address is completed by Clara (we suppose) although the signature appears to be Mary Marsh's.
So what happened?  Did Clara simply make a mistake when she was entering her information?  
Update 21 May 2018:
Clara DID marry but the confusion is that she married someone with the same surname, which is why it looked odd on the 1901 and 1911 censuses that she was recorded as a widow. She did, in fact, marry her first cousin John Richings, son of Alfred's brother James.
Sheila

Clara married John Richings on 4 Jul 1889 in Church of St Mary and St John, Cowley, Oxfordshire, England. John (son of James Richings and Kezia Stallard) was born in 1857 in Oxfordshire, England; died in 1895 in Headington, Oxford, England. [Group Sheet] [Family Chart]