Cornelius developed a passion for fine mechanics as a young boy,  when he taught himself to repair watches for his classmates at school in Yorkshire, England. He went on to complete an apprenticeship in watch and clock making in Switzerland.

In 1977 he won both the Swiss watch making championships and later that year won a gold medal at the World Championship in Holland. In December 2012, he was promoted to a Fellow of the British Horological Institute, United Kingdom.