H e walks! He talks! He breathes! For most people, Morgan McSweeney is a quasi-mythical creature. A being that exists almost entirely in the shadows. If at all. Away from the public gaze. The legendary slayer of the Labour left, rumoured to have been shaped in the dark arts by Peter Mandelson, who went on to become the eyes and ears of the prime minister. Possibly even his brain. It was often said the only ideas Keir ever had were ones he had been force-fed by Morgan the Mighty. But on Tuesday morning, Keir Starmer’s former chief of staff was forced out into the open, summoned to Westminster to give evidence to the foreign affairs select committee about the appointment of Peter Mandelson as US ambassador. McSweeney looked far from happy at the exposure. Head down, no eye contact with the public as he sped down the corridor. Maybe he was worried about being out and about in daylight. The darkness has been kind to his skincare regime. He looks far younger than his 49 years. His nerves were evident.…