On 05 Jun 1798 Luke Gardiner 1st Viscount Mountjoy (age 53) was killed in action at The Battle of New Ross. His son Charles John Gardiner 1st Earl Blessington (age 16) succeeded 2nd Viscount Mountjoy, 2nd Baron Mountjoy.

On 25 May 1829 Charles John Gardiner 1st Earl Blessington (age 47) died of apoplexy without issue. Earl Blessington, Viscount Mountjoy, Baron Mountjoy extinct.