The company said that this was due to Aikenhead having achieved his objective, of introducing improvement programmes to transform the business.
Non-executive chairman, Gavin McAlpine, said: “We would like to thank Tony for his significant contribution to the business. He has seen the company through a major process of transition, which has moved us back into profit this year.”
The company also announced that the process of succession planning is underway and that it will be appointing a new chief executive.