I do not have Charles Mitcham in the 1881 census as by then, Sarah was deceased and the children were with John Wilkinson, a couple of streets away. As I said 'If I have John Wilkinson in a census then I do NOT have Charles Mitcham'.
John and Charles both claim to have been born in Cambridgeshire.
Whenever I have found a Charles Mitcham in a census after 1871, that could be a match he is always said to have been born wherever he happened to be living at the time but I have never been able to find birth records to confirm it.
Further to that - all the children fathered by Charles Mitcham and born in Essex or Mile End were said to have been born in Cambridgeshire once they were living with John Wilkinson in 1881