When watching a slideshow on the First World War that Ken presented, he told him that his own grandfather was in that conflict but go into trouble when he deliberately mis-named a Howitzer gun as a "Hows-your-father" gun and was later cheeky when Ken advised on good television programmes to watch and he replied that he'd rather watch Sylvester and Tweety-Pie.
In April 1972, Mark was caught by headmaster Wilfred Perkins writing "Barlamb fancies Terry Bate's Mam" (sic) on the blackboard (referring to deputy head Ken Barlow and Rita Bates). When questioned by Perkins, Mark tried to blame another pupil, Susan, for putting the idea in his head.
In October 1973, Len Fairclough stopped Rita Littlewood from selling fireworks to Mark and his friends at The Kabin and barred the lads from the shop. Mark later went to watch the communal bonfire with his friends. There, a freak accident occurred when a spark landed in an open box of fireworks, setting them off and setting Mark on fire. Ken Barlow rescued him by smothering him with his jacket but Mark was seriously hurt and had to have a skin graft on his leg.
While in hospital, Mark was visited by Albert Tatlock and two school friends. Albert used the toy tanks the boys were playing with to launch into a discussion of the First World War. The boys were interested in what Albert had to say and Mark already knew that it was that conflict in which tanks had first been used. Alan Howard blamed himself for the accident as he was supervising the fireworks. He stayed away from the hospital at first out of guilt, but after Albert scolded him for doing so, he at last visited the boys, giving Mark a toy Alfa Romeo and Lamborghini he'd promised him. Mark was discharged from hospital the following week.
- The character was not credited under his name until the April 1972 appearances onward.