Kay was born in 1778, son of James Mangnall (LM022) and Richmal Kay (LM023)

Kay became an Cadet in the army of the East India Company in 1795, was appointed an Ensign on 18th February 1796 and then a Lieutenant on the 7th May 1797. On the 17th January 1797 he was appointed to the 1st Battalion 4th Regiment from the 2nd Battalion 4th and he served with them until his death in 1801 during the Second Poligars War. Kay was killed in action on the 31st March 1801 at Panjalamkurichi. Kay was buried at Panjalamkurichi in a cemetery near Gavunagiri village in Ottappidaram Taluk.

There is a memorial stone with the following inscription:

Sacred to the memory of Captain john Campbell, Lieutenants A. Campbell, D. Gilchrist and P. Shanks of H.M. 74th Regiment, Lieutenants J. Spalding and A. Campbell, H.M. 77th Regiment, Lieutenant M. Egan 1st Battalion 3rd Regiment N.I., Lieutenants W. Fraser and K. Mangnall 1st Bn. 4th Regiment N.I., Lieutenant C. Torriano, 1st Bn. 9th Regiment N.I., who bravely fell or died of wounds received in the assaults on the fort of Punjalemeourchy, on 31st March and 24th May 1801

There are some documents that suggest that Kay was a Colonel and served with “his cousin Robert Clive” but these are probably embelishments added by the family!