Mark Thomas grew up in Cardiff and was educated at the University of Cardiff and the London School of Economics. He is a founder member of the Celestia Action Group and Welsh Cladiators, and has been elected three times as the Chair of the Celestia Management Company representing 457 leaseholders. Like other self-employed victims, Mark purchased his property in Celestia Cardiff Bay in 2007 as part of his retirement plans, which are now seriously disrupted. He has been battling Redrow and trying to influence the Welsh Government daily since 2019. In addition to organising Welsh protests at Redrow sites in Cardiff, the Senedd, Westminster, and the Swansea Maritime area, he has written articles on the crisis for the Institute of Welsh Affairs, the Leasehold Knowledge Partnership, and Welsh Housing Quarterly.