[1] Fenton-Cawthorne was born in 1753 to Elizabeth née Cawthorne and James Fenton of Lancaster, a barrister, and educated at Queen's College, Oxford (1771) and Gray's Inn (1792).
He was first elected as an MP for Lincoln in January 1783 and was an opponent of the abolition of the slave trade.
[2] On 27 November 1795, as Colonel of the Westminster Regiment of the Middlesex Militia, Fenton-Cawthorne was arraigned before a court-martial on 14 charges including that of embezzling "marching guineas" paid to militiamen of the British Army.
Found guilty on seven of the charges, he was cashiered as "unworthy of serving His Majesty in any military capacity whatever"[3][4] having "acted fraudulently and in a scandalous and infamous manner".
His older brother also entered Parliament at the same time as MP for Fife.