In 1820, Ellis was commissioned as a Captain of the 14th Regiment of Militia for the County of Surrey, England. He had retired from that position when, on 18 December 1829, Ellis met the vessel, James in Kingstown Ireland and joined the other passengers for the journey to the Swan River Colony. He arrived on 8 May 1830 and 'selected land in the Avon district.' Ellis was appointed Resident Magistrate (or Government Resident) at Kelmscott in September 1830 and in a letter dated 1 December 1831 wrote to the Colonial Secretary with the names of 'persons fit for the purpose' of serving as 'Yeomanry Cavalry' who would be able to follow 'the lines of conduct towards the native' required by the Colonial Secretary. It is not clear whether 'Yeomanry Cavalry' were actually appointed in Kelmscott. Ellis gives his residential location as Kelmscott and his age as 48 years in this letter.

The contents of a letter written by Captain Ellis gives his account of conditions onboard the ship James which brought him to Australia. The WA Museum's maritime history site provides the following information about this journey and its aftermath:

James was an American-built vessel owned by Chapman and Company. The vessel was sheathed in copper (1828), carried two chain and one hempen cable, and was armed with three cannon. It had a single deck with beams, a raised new deck and new upperworks in 1828. The vessel was involved in the passenger trade from Europe. Captain Ellis met the vessel at Kingstown, Ireland, on 18 December 1829 and described the conditions aboard:

I found her crowded with passengers [of] the class of labourers, men, women and children, whom with passengers taken in at Kingstown, made the ship's crew 84 persons, and a quantity of sheep, pigs and geese... There was no place for goods, provisions etc. part of our accommodation was filled up with stores and luggage belonging to the ship. .There was scarcely enough room for 24 persons to eat and sleep... We therefore suffered great inconvenience and want of air particularly as the height between the decks in the greater part of our cabins is but 4'6" between the beams and 4' to the beams instead of 5'6" as required by Act of Parliament (Particulars of the Voyage from Kingstown Ireland (to Swan River in 1828 [sic] per brig James) of Capt. Ellis et al., quoted in Henderson 1980:101-2).
The journey was very difficult for all on board the vessel and Ellis demanded that a survey be made of the vessel once they had reached Bahia (Salvador). The captain of James, Goldsfield, refused the request, and conditions continued to deteriorate. Five people died before 4 March 1830. James finally reached Swan River on 8 May, with twelve crew and 74 passengers and moored at Owen Anchorage.

Whiteley reports that Ellis was appointed 'superintendent of police' in 1832. Whether this was a position different to that of 'Principle Superintendent' of the mounted police to which he was appointed not long before his death is uncertain.

Trove gives Ellis' birth year as 1782, but in a letter dated 1 December 1831 he gives his age as 48 years. It is therefore possible that his birth year was 1783.

Chronology

September 1830 - ?

Resident Magistrate (or Government Resident), Kelmscott

1832 - ?

Superintendent of Police

1833 - 11 November 1834

Superintendent of Natives

1834 - 11 November 1834

Principle Superintendent of the Mounted Police