Duncan comes to Sun Hill from Epsom and his motives for wanting a transfer to the East End are at first a mystery to his new colleagues in CID. A bulky Glaswegian with an ironic sense of humour, he quickly makes his presence felt, particularly with the women in the station, whom he treats with a combination of appreciative chivalry and old-fashioned sexism. Duncan manages to combine an air of profound laziness with sudden bursts of enthusiasm If he senses the chance of a good arrest, he pursues a case with dogged determination.
There is nothing he enjoys more than arresting a villain, and he thoroughly annoys his victims by treating them with immense affability. Thirty-nine years old, with twenty-one years' service behind him, Duncan can be irritatingly smug about his experience of the job, an inveterate tease and, when roused, witheringly accurate in his put-downs, but his ready wit wins him friends and allies in the station. He is not as impulsive as some and often acts as the middle-man preferring to see both sides of an argument.
The chink in his armour is his wife, Shona, who he treats with a healthy degree of respect and secretly adores, until she has an affair and leaves him. Shona is a highflying career woman, working for one of the larger financial institutions, and it is her salary rather than Duncan's that pays for their Docklands Riverside apartment. When Shona says jump, Duncan's only question is how high, a fact that his colleagues come to understand when they realise that it is her job that dictated the move to Sun Hill. Duncan is beginning a life on his own and slowly beginning to realise that he is up for standing on his own two feet.
One step ahead of the game, Duncan decides to move onwards and upwards, becoming part of the Murder Investigation Team. One of his first assignments brings him back to Sun Hill to investigate the Sun Hill serial killer, with Acting DISamantha Nixon.