0151 4960293 is not a real number it is a phone number that was made up for TV. The telephone number is provided as the telephone number for Mark’s parents in episode 1 of a BBC series called Time. The number is provided to Mark by his wife as the contact details for his mum and dad.
Unfortunately on his first day in Craigmoor Prison he is only permitted to make one telephone call. He chooses to call his wife as he has does not have his parents number to hand. His wife promptly reads out the number to him.