Hello Di,
William S. Aggs was my GG Grandfather. He was born in Camden Town, London, England and emigrated to Australia in 1863, worked as a butcher, married Elizabeth Ash Cory Fox on 15 March, 1871 and they had 10 children. He died on 16 April, 1916 in Sydney. His parents are listed as William Aggs, Inspector of Police, and Ann Spurgin.
As for the larceny (theft) conviction it doesn't sound like "Crime of the Century" and in those days it was common for an apprentice to live with his master. I understand that Australia was looking to build up its population with skilled immigrants so he may have seen a chance for a better life. If he was an assisted immigrant then more details about him would have been recorded than if he paid his own fare. If he was a member of the ships crew then that could have been a way to pay off his fare.
William & Ann Aggs and their children were listed on the 1851 Census Form. The Parish/Township was Hammersmith, Ecclesiastical District of St Paul in the City/ Borough of Middlesex. It states that William Aggs, aged 49 years and Head of Family was born in St Pancras, Middlesex. Ann, his wife, was 38 years and it lists six children - Ann Emily, William, Harriet Martha, Henry James, Louisa Alice and Alfred John. Also listed in the same house was Harriet Spurgin, aged 26 years and William, aged 48 years. I'm not sure what happened to any of them except William.
I don't have a copy of the parents marriage certificate from 1838 and am interested in finding out about what came before. Your posts have filled in some gaps and if you have any more then I would be interested in learning about it. Cheers.