Dr. John Maunder Gill may have been the son of John Maunder Gill of the 46th regiment who was in Sydney prior to 1817 and died in Glamorganshire, Wales in 1823, although there is no mention of a son in his Will dated 19 July 1813.
His leased estate near Murrurundi was known as Bickham and had previously been a grant to John Johnson Cory (son of John Cory of Paterson) who died in 1839.
In December 1841, John Gill accompanied Magistrate Edward Denny Day when he led a determined pursuit party to track down a desperate band of bushrangers known as the 'Jewboy gang'. The Jewboy gang had terrorized Brisbane Water and Hunter Valley districts for months. John Gill joined the pursuit party when they passed through Murrurundi. Others who joined the party were Edward White, Richard Dangar, Mr. Warren,
William Shinkwin and several ticket of leave men - Walker, Evans, Peter Dawe and John Doran. They surprised the bushrangers at Doughboy Hollow near Murrurundi where they found them casting musket balls, and after a brief battle the notorious gang were captured. This did not however, put an end the lawlessness of the district which was notorious for cattle duffers and thieves.
In 1843 the district had only one Magistrate and John Gill's name was raised as a candidate - As licensing day is fast approaching, and we have only one unpaid magistrate at Murrurundi his Excellency the governor would confer an obligation on the inhabitants of this district, by appointing another, as three magistrates are required. We know of no gentleman residing in our district better calculated for the office than Dr. Gill of Bickham, a gentleman of independent principles and strict integrity. We should be glad to see him administering justice on our bench. 
As well as his pastoral pursuits at Bickham, John Gill attended to medical duties and in 1841 he testified at the inquest of George Clerk. He played an active role at the race meetings in the district and was steward at the Page's River Races in the 1840's.
John Maunder Gill moved to the Tamworth district in 1850. He died on 5th February 1858 at Moonbi near Tamworth. His widow Elizabeth Mary Gill gave birth to a daughter on the 17th September 1858. Their eldest daughter Sarah Mary died age 19 in 1875. Elizabeth Mary Gill died in England in November 1884.
Many years after his death John Gill was still remembered throughout the district. A correspondent to the Maitland Mercury wrote of him:
The Haydons and Brodies were the great landed proprietors of Murrurundi in those days, and Mr. Warland owned the Harben Vale estate. Mr. Cory's Bickham estate was let to Dr. Gill and Mr. Edward White - who was a brother of Mr. (James)White of Edinglassie. The partners were extremely popular in the district. Dr. Gill was a personal friend of my own; he married Miss Webb, a famous beauty, related to the Littles of Cressfield. He bought the Moonbi Station and died there. He has lain in Tamworth churchyard for many a long year, yet I can still recall at will the soldierly, stately figure, the dark curling hair, and flashing hazel eyes of John Maunder Gill. 
Notes and Links
1) Marriage of John Gill of Moonby near Tamworth to Elizabeth Mary, eldest daughter of the late John Webb of Sydney on 14th June. Minister Rev. Edward Williams - Maitland Mercury 24 June 1854.
2) John Mander Gill (senior) of the 46th...... Sheffield silver salver inscribed on underside 'To Capt. Gill (senior) By his Friend Capt. J. Wallis 46th Regt', 1817 - The maker's mark is that of James Ellis and Co., whose mark was first registered in 1793. The inscription is a dedication from Captain James Wallis, Commandant of the Newcastle penal settlement to his friend and fellow officer, Captain John Maunder Gill. Both were officers in the 46th Regiment and had joined the regiment as young men in the early 1800s. Both had served as ensigns in the West Indies against Napoleon's forces and both took part in the famous battle of Dominica in 1805. By 1813 when their regiment sailed for New South Wales, Wallis and Gill had risen through the ranks to become captains. Gill became Acting Engineer for the colony soon after arriving in Sydney up to his departure in December 1817......State Library of New South Wales
5). Biraban was born about 1800 at Bahtahbah (now Belmont) into the Hunter River Lake Macquarie language group. He acquired his English name John McGill (M'Gill) from Captain Gill (John Maunder Gill senior), who brought him up at the Military Barracks in Sydney, and took his totem name Biraban (Eaglehawk) at his initiation in 1826. Biraban is best known as the language informant of theReverend Lancelot Threlkeld, a Congregational minister, who in 1824 established a mission for the Aboriginal people at Ebenezer (Toronto) on Lake Macquarie. Threlkeld described Biraban as 'a noble specimen of his race, my companion and teacher in the language for many years' 
Biraban portrait (John McGill) by artist Mr Alfred T. Agate from the The U.S. Exploring Expedition of 1838-1842
6) - Native Dog Hunting......Liverpool Plains. Dr. Gill's fox hounds threw off at 'Warrah', where a party of tip-toppers had assembled determined on sport; horses and dogs in prime order, the nature of the country and state of the weather being favourable beyond comparison. The hounds first threw off at 7am. The dingo, being liberated from his bag, in good trim, and allowed five minutes' law, was well followed by all hands, stimulated by the glorious harmony of the pack, and after a run of about six miles in fifteen minutes, was killed amidst the death - whoop of the field. Having camped, to breathe the dogs and partaken of refreshments and 'nobblers' round, the hounds started on a fresh scent, and after a short run, gave full cry at a hollow log, in which six well grown pups and their dam were discovered by the vigilant eye of Mr. Wyatt, who suggested to his companions that they should be instantly spiflicated, in which suggestion , all parties concurring, they were, by the aid of a tinder box subjected to that effectual punishment to which the Hindoo widows are so ungallantly doomed. Another halt - more grog - and fresh determination, having revived the party, the hounds were again brought to the scratch, and after a few checks started on a warm scent. After a glorious burst of a few miles, several rasping logs having been cleared by the eager sportsmen, a full grown native dog was come up with and died. 'Home sweet home now echoing from the huntsman's horn, our horses' heads were turned in obedience thereto, after a day of unclouded satisfaction.