Robert Hulse from The Brunel Museum said: "From the station platform visitors can see the pillars and portico of Brunel’s magnificent grotto, stretching under the river. The archways are now empty, but they once held shops, tightrope-walkers, sword-swallowers and fire-eaters in the world’s first underwater fair!"
Both the steam train rides and floodlit tunnel tours are free. Brunel Museum are also holding £5 tours of the Grand Entrance Hall, a secret underground chamber, where you can descend a temporary staircase into a huge underground space half the size of Shakespeare’s Globe. For more information on all these events, visit the Museum's website.