One feat of engineering in this project was the opening of Box Tunnel, designed by Brunel, in 1941. He was known to have a sense of humour and for many years it was speculated that he had designed to angle of the tunnel such that on the early morning sun would shine right through from East to West on his birthday, 9th April.
Recently this theory has been questioned with an even more intriguing alternative theory proposed in its place. See: Emma Joan Brunel.
The rail bridge had been built in 1839 and was designed by IK Brunel.