After graduating in economics, Gren joined the NHS as a management trainee. He moved to Wales in 1983 and held the post of CEO of Conwy and Denbighshire NHS Trust for 17 years until he retired in 2009.  Since then he has provided consultancy support to NHS Trust Boards in the UK on patient safety.  Gren lives in Prestatyn and has been involved in a number of local charities including Marsh Tracks, a cycling facility in Rhyl and the North Wales Resources Centre for disabled people.  Gren joined the Board of St Kentigern Hospice in February 2022 and is chairman of the General Purpose committee, and sits on the Finance Committee and also advises on good governance practice.