Sebastian Bleasdale was brought up playing games such as Enchanted Forest and Dominique. He stopped playing games until his late teenage years when he stumbled upon The Settlers of Catan and Tigris & Euphrates and stepped cautiously into the world of designer games. These two purchases were followed by Simply Cosmic which he liked considerably less. This led him to design his first game in an attempt to create a better version - an attempt that ended in failure as the game was abandoned half way through the first (and last) test.

In 2001 he graduated from Cambridge University, and his job took him to Windsor, where he met and started playtesting for Reiner Knizia. His playtest experiences led Sebastian to realise that the first versions of games were (almost) always sub-par, and inspired him sufficiently to take up the mantle of games designing once more. At the present time, Sebastian continues to work with Reiner on a number of projects, and has designed a number of games, of which On the Underground is the first to be published.