In the light of your further comments above, Pingu, I had another look further on in the 19th century. There was only one marriage registered in Devon between 1861 and 1901 between a Nicholls and a Hart. That was between Amos Andrew Nicholls, the grandson of the Amos born Redruth in 1787, and Charlotte Lucy Hart, daughter of John Hart; she was born Dawlish (Newton Abbot to be exact) in 1853. John Hart her father was a shoemaker, born Ashcombe in 1800. The family were living in Chelsea in the 1891 Census and in Paddington in 1901 and 1911. Amos was a house decorator.
This doesn't tie in with family legend, but in my experience family history seldom does!