Arthur Henry TRAPNELL birth registered Sept qtr 1859 at Bishops Storford has mmn BARRY, but I find it hard to believe he is John and Louisa's son - though it seems to say that on the 1861 census. 
I can't seem to find the birth registration of the Fanny TRAPNELL (aged 6 on the 1861 census).
I think the 1790 which seems to be commonly listed as the year she was born must be wrong. The 1851 census lists her as 35 years younger than the 1861! And the article you found seems to be the missing piece, as that lists her age as 55 in 1869, making her DOB closer to 1817 (as per the 1851 census) than 1790 (as per the 1861 census). That means her children were born when she was approx 20-40, which makes more sense.
