Arthur was born on July 5th, 1856 at St. Blazey to John and Louisa (nee Trevethan) Trewin. His father, who came from Portsea, Hampshire, was a watchmaker and general dealer and Arthur followed him into the trade serving his apprenticeship with his father. He married Annie a native of Tavistock, in 1885 and the following year their daughter, Winnifred was born at Tavistock. Arthur first started his own watchmaking/jewellery business in 1891 running a shop at 50, Portland Street, Exminster, St Sidwell, Devon. In 1895 another daughter arrived called Margorie Lousia (who would go to marry Fred Philp in 1923, who himself then became a business partner to Arthur in his business). By 1901 the family had moved back to Cornwall, where Arthur set up shop running a jeweller/watchmaker/gunsmith business at 19, Westgate Street in Launceston. His wife Annie died in the March of 1922 and Arthur survived her by nearly 26 years, passing away at the ripe old age of 92, in the December of 1948. The business was then carried on by Fred until his death in 1951.