Aged about 34 when he deposed his uncle, Donald III, with English help, Duncan was in effect an English vassal and, as such, he was unpopular in Scotland.
Duncan was killed by the Mormaer of the Mearns on 12 November 1094, presumably at Donald's instigation. His reign had lasted for about six months. It was he who granted the earliest surviving Scottish charter.
The eldest son of Malcolm III by his first wife Ingibjorg, Duncan spent 15 years as a hostage in England before being released by William II in 1087.
