MacDiarmid, who led ScottishPower through the deregulation of the UK energy market, will also chair the SMS remuneration committee. Nigel Christie, who has been a non-executive director with SMS since the company's AIM debut in 2011, is retiring from the board. Miriam Greenwood will now taking over as chair of the company's Audit Committee. Commenting on the board changes, SMS chairman, Paul Dollman, said: "The Board would like to thank Nigel for his very significant contribution to the company. "He has been involved with SMS since before the company was listed on AIM in 2011 and has provided invaluable advice and support through the years. We wish him every success in the future. "We are delighted to welcome Willie to the Board and look forward to working with him. "His considerable PLC experience in the energy space and with ScottishPower's metering activity will be invaluable as we grow the business in the electricity sector."