When travelling with Dickens, Fitzgerald noticed that he often appeared uneasy during a train journey, especially if there was a sudden halt and even more so if the train "came to a stoppage in a tunnel".
After one such incident in Ireland in May 1869, he wrote to Dickens asking how he was feeling and received the reply:
rest and a little care immediately unshook the railway shaking
These reactions of course, stemmed from Dickens' experience in the Staplehurst rail crash of 9 June 1865.
Fitzgerald was one of a few intimates who was invited to Gads Hill immediately after the crash.
Illustrated London News June 17 1865 p. 572 MAC local Studies Collection