Rumour has it that Henry was the brother of Roger de Mortimer the same Mortimer who became Queen Isabella's lover and who was instrumental in the deposing of Edward II.  Not much is known of Henry's earlier life however it is said that he managed to gain favour at the English court through his father's connections with the church. Henry soon became disenchanted with Edward II's court and detested Edwards close friend Piers Gaveston so much so that he wished Edwards downfall in favour of his son. Through his fathers church he learned of a man Sir Aidan de Culter who was close to some of the Scottish magnates. Sir Aidan introduced Henry to Sir Harry de Brechin, both men had the same view on Edward II's regime and entered into a pact. Henry would learn all he could about English intensions for north of the border and pass on this information to Sir Harry who inturn could advise Robert the Bruce.

Sir Harry sent one of his men David de Brownhill to help Henry spy on Gaveston however Gaveston had learned of this and paid de Brownhill to trap and expose Henry as a spy. Henry was caught and imprisoned, cursing that one day he would have revenge on de Brownhill and his pay master Gaveston.

Fortune favoured Henry for he was rescued by Tristan Moir who helped him expose de Brownhill for the traitor he was. Tristan delivered Henry into the care of Margaritte Dubois until he recovered from the strains of his imprisonment. Margaritte was a widow and both became very close during Henry's recuperation. Henry swore that he would return to Margaritte after dealing with his enemies. After making contact with Sir Harry he learned of the full treachery of de Brownhill and with the help of Sir Aidan's mentor Michael Beckett exposed Gaveston's treachery to the English barons who in turn managed to have Gaveston banished and subsequently executed.

After Bannockburn and the return of better relations between Scotland and England Henry rejoined Margaritte at her lands at Sherrifmuir , he later through his marriage to Margaritte  became justicier  of the peace. It was while carrying out his duties a common horse thief was brought before him on trial, it was none other than David de Brownhill, who had resorted to horse theft to stay alive. Now Henry could take revenge, however rather than anger he felt pity for the poor wretch who stood before him, he sentenced de Brownhill to feudal service without pay within Sir Andreas of Thurso's household. In later years Henry together with his wife travelled all over Europe using his skills as a justicier to ensure that trials were conducted fairly.