The Trewartha surname began in Cornwall, the most south-western county of England, at a time when mining, specifically tin mining, dominated that area’s economy. Here are the distributions of the name in the UK according to the electoral registers of 1881 and 1998 (click for larger images)

(‘Trewartha’ clearly is not unique in spreading like this — it is a common feature of the 20th century that names and genes have spread far and wide as we as a species roam more widely, more quickly than ever before, for obvious technological reasons.)

So specifically it started around the (now) city of Truro, where Tin was being produced as early as the 1200s. The city’s Coinage Hall was originally built in the 1300s, and then rebuilt in the 1800s. It now houses a tea room and pizza restaurant. The Hall was where tin was stamped and sold around the world.

If you travel around these places you’ll find plenty of places, and even some people still, called Trevarth, Trevarthen, Trethowan, and of course Trewartha. Going back 4 generations takes my family to Chapel Porth (public photos on flickr.com of Chapel Porth) — 2 miles from St Agnes. Here’s a
long article on the history of mining around St Agnes.

Including this information on migration:

The Coinage Laws were finally abolished in 1838, resulting in considerable effects on the Smelters who sought to maintain their control by any means against depression in the Cornish mining industry, plus increasing competition from abroad. The late 1830s into the 1840s was the key period of migration of Cornish mining families, not just to other mining centres in the UK but to Cuba, Australia and Tasmania. Advertisements were everywhere in Cornish newspapers by 1839 advertising mining positions in the New World. Emigrant ships rapidly started to sail from Cornish ports such as Penzance, St Ives, Hayle, Padstow and Fowey, many of which were head to Quebec and New York in North America

Shorter BBC article about the history of tin mining.

Although my name labels my Cornish roots, I was born in Devon in 1947. For 18 years I lived in a small village called Ide, close to the City of Exeter, but far enough away for it to be a separate community.

I was the youngest of three, with an older brother, Mark, and a sister, Angela. My father, who died in 1981, was brought up in Newton Abbot, in Devon. My parents met in Chapel Porth, near St Agnes, as my mother, Mary Coleman, lived there with her parents, Thomas and Ada Coleman, close to her maternal grandmother, Elizabeth Beck née Bennett from Yorkshire.

My father is connected to Chapel Porth through his mother’s family – the Lawrences. My great great grandfather, Mark Lawrence, was Captain of the Wheal Lawrence mine not far from Wheal Coates. Our Trewarthas all have Truro-based connections as well with my paternal grandfather being a local trader.

Wheal Coates: home of the Norkins

At the age of 11 I attended Exeter School, in Heavitree, between 1958–1965 and completed undergraduate and graduate studies at Swansea University to become a probation officer (PO). I worked as a PO for ten years in the north of England and as a child protection officer for another six years before moving to Dundee University to teach on their Graduate Social Work programme.

I have lived and worked in London since 1996 having retrained and qualified as a counselling supervisor and chartered psychologist.