By sheer coincidence I was reading about the history of Lemmings just a few days ago (is a good read). Russell was responsible for the game concept and name of the iconic game which was ported to many platforms and is estimated to have sold over 15 million copies.
DMA (which since a takeover is now known as as Rockstar North) will perhaps be better known to younger readers as the creators of the Grand Theft Auto franchise. Russell went on to found Visual Science Ltd who were responsible for the PlayStation version of the game.
If you are interested here is an interview with Russell Kay albeit a few years old. I think this development is the most exciting to happen at YoYo Games for a long time – possibly ever – as it demonstrates that they are serious about substantially developing the Game Maker brand.