He was Trevor's driver prior to the traction engine being sent to Crocks Scrap Yard to be cut up. After Edward convinced the Vicar of Wellsworth to help, Jem restored Trevor and demonstrated him to the Vicar and his two sons. Thankfully, the Vicar was able to buy Trevor cheap, and continued to hire Jem's services as a driver and mechanic whenever one was required. He also tutored the Vicar's eldest son on how to drive and maintain Trevor.
Jem, along with Farmer Trotter and others, was a part of the rescue team which found Duke. He seems to be very knowledgeable about road steam traction, as he has also driven George. Jem Cole is a skilled mechanic, as shown when he restored Elizabeth and an old narrow gauge coach into a Refreshment Coach. As of the eleventh season, he appears to be working as a farmer and has grown a grey beard. In the fifteenth season, he was seen fishing with a little boy in the Whistling Woods; this could possibly be his son or grandson. In Day of the Diesels, he helped to extinguish a fire at a barn. In the sixteenth season, he helped to put out another fire, this one being at Sir Topham Hatt's Shed.