The Thunder Child was a fictious ship, created by H.G Wells in the seminal invasion story, The War Of The Worlds.
It was an Ironclad ship, specifically a "Torpedo Ram", an unsuccessful attempt to crossbreed a cruiser and a monitor. In reality only one such ship was commissioned, named the Polyphemus.
They were called "Torpedo Rams" because (Surprise, surprise) they had both torpedos (Five, in the case of the Polyphemus) and a Ram, in the stlye of a Greek Trireme.
The Thunder Child was tasked with defending a convoy of steamers departing London, laden with refugees, against an encroaching Tripod taskforce. In this it succeeded, destroying one Tripod and immobilising a second before being utterly destroyed.

If I may break objectivity for a moment, the role of HMS Thunder Child illustrates a key dichotomy between the British and the Americans:
To put it bluntly , we rock. In every English version of War of the Worlds, several Tripods were utterly destroyed by the sheer badass-ness of the British army. However, in the American renditions, the enemy are seen as utterly unassailable,unless you're Tom Cruise a cultural hangover from the days of resisting the all-conquering British Empire.Or not, whatever

Just kidding America, I love you really.