Bob Rankin has resigned as chief executive of Lilley after four years with the company.No immediate reason was given for his departure, although a friend of Mr Rankin said: 'I think he just got fed up with the way the industry was going and wanted to spend more time on his farm.'In a statement, Lilley's directors said they 'paid tribute to his energetic contribution to the group's development since his appointment in September 1988 and record their good wishes.'Lilley has not filled Mr Rankin's position. Instead, the firm has appointed James Hann, the 59-year-old part-time chairman of Scottish Nuclear as deputy chairman. Mr Hann will share the chief executive's role with Sir Lewis Robertson.