I remember ,when I was firing on BR, sitting in the loop at Moor street waiting for the road through Snow Hill tunnel and one of those little monsters came by us with a "tripper" from Bordesley yard ,going north, with a huge train maybe 40 wagons and vans. Really "going for it " continious sparks out the chimney, steam under the boiler from the spindle glands and blowing off! Those engines boxed well above their weight. Never worked on one but must have made an impression on me 'cos that was in about 1964! Happy days!