Stuart - I came accross a chart which I received some time ago which shows that my great grandmother, Sarah Derby, whose father was Alexander. He had had a sister, Elizabeth, who married William Loudon. This must be your connection. I dont know how this was proven as the records are not very good here. I would be very interested to know your line of descent, for the record and if you have many relations in Australia. I have a book, which I treasurebelonging to a Thomas J Derby, cousin of my grandfather, dated 1873.