43020 slowly leads the 1A43 11:57 Cardiff Central to Paddington service from the up line onto the down line via the crossover at Bourton on 16 February 1984. It will now proceed 'wrong line' as far as Uffington. The Great Western Mainline is fully bi-directionally signaled, but this is one of the few times that I have seen it in use. The up line was closed for emergency repairs after a freight train derailment the previous day between the site of Knighton Crossing and Uffington. The fog had just started to lift, leaving all the trees and bushes covered in ice.