Possible Clues:

• Mark joins Home Counties to run as athlete
• Dash specialist
• At last he does his type of work at top speed
• A second Caxton, perhaps, and no slowcoach
• Second person making impression, one in the 100 metres
• Track star, perhaps
• One runs with scoop, originally going to press
• Small person making an impression as an athlete
• Bolt, say, in small piece of office equipment
• Rapid runner