From 2002 to 2007 Lewis was the Crown appointed Scottish Public Services Deputy Ombudsman and a member of the Executive Board at the Scottish Public Service Ombudsman.

He is a priest in the Scottish Episcopal Church, served congregations in Motherwell, Shetland and Dumfries and was a canon of St Andrew's Cathedral Aberdeen.

He was a member of Shetland Islands Council from 1990-1999, and Convener/Leader from 1994-1999. He is a former Vice-President of COSLA and represented the UK on the European Committee of the Regions. He was on the Executive of the Constitutional Convention and a member of the Highlands and Islands Convention.

He was Chair of the Management Committee of Shetland College, served on the UHI Steering Group, was a Director of UHI Ltd and has been a board member or trustee of a number of organisations including Scottish Homes, and Dumfries and Galloway College. He is a Fellow of the Royal Society of Arts.

Lewis joined the Ombudsman Services as Chief Ombudsman and Chief Executive in 2009. He is responsible for the quality and consistency of the final decisions made by the ombudsman team.