The Return of the Kettle?

This Guardian article outlines the proposed high tech steam locomotive proposed for charter work, with a maximum speed of 125mph.

The 5AT will resemble a conventional Stephensonian steam locomotive, yet it will be neither smoky nor grimy. Yes, it will produce that familiar rhythmic beat, those plumes of white steam; its piston rods will race in and out of visible cylinders, and its tall disc wheels will be driven by a form of reciprocating motion invented by the Belgian engineer Egide Walschaerts in 1844.