Career
He purchased the seat from John McCausland of Strabane for £2,000 after the death of the incumbent Robert Lowry when a new writ was issued for the borough on 22 October 1765. Subsequently he represented Cavan County in the Irish House of Commons from 1768 until his death in 1787. The Cavan poll result on 2 August 1768 was Maxwell 727, Montgomery 648, Pratt 570, Newburgh 402.
The poll finally closed on 11 November 1768 and the final poll was Maxwell 927, Montgomery 739, Pratt 668, Newburgh 451.
When the new Parliament met in 1769, Mervyn Pratt, the defeated candidate, petitioned against the election of Montgomery on grounds of bribery, corruption and undue influence. This petition was not finally determined owing to the premature prorogation of Parliament in December 1769, so Montgomery survived and continued to represent the county until his death.
He had previously stood as a candidate for Cavan in the 1761 general election but was defeated. The youngest son of George Leslie Doctor of Divinity, (Rector of Clones & Kilmore) and Margaret Montgomery (sister of Colonel Alexander Montgomery (1686–1729) of Convoy House, County Donegal and Ballyconnell House, County Cavan).
He was in the inner circle of the Irish Parliament but his low-church Northern background clung to him and whilst he became a general of volunteers and supported Flood, he opposed any relaxation of the laws against Catholics.
"The Irish Parliament 1775" states- "He obtained a Barrack Master"s place £150 per annum, for his Friend. On some few Questions during Lord Townshend"s Administration He voted with Government. In Lord Harcourt"s Administration He has been constantly against, and hates all Government.".
