The chief executive of energy firm Scottish Power has resigned unexpectedly.
Nick Horler is leaving the Glasgow-based company after two years of integrating the firm with its Spanish owner, Iberdrola.
He has also played a key role in boosting Scottish Power's investment in renewable energy.
Despite his resignation, Mr Horler, 51, is expected to remain as an adviser to Ignacio Galan, the group's chairman.
His resignation was accepted at a board meeting of Scottish Power in Glasgow on Tuesday, which was attended by Mr Galán.
The board also includes Sir Tom Farmer, Lord MacDonald of Tradeston and Lord Kerr of Kinlochard.
In a statement, the company said it would name "a new executive responsible for the company", who would need to have an "appropriate profile".
Until this appointment is made, Scottish Power will be run by its current management team, supervised by the group's international chief operating officer, Amparo Moraleda.
Mr Galán said: "The UK subsidiary is today a much more efficient company as a result of Mr Horler's efforts."
Scottish Power became part of the Iberdrola Group in April 2007.
Mr Horler, who is from Newcastle, joined in June 2008, recruited from E.ON, where he had spent 10 years, rising to become its UK executive director.
Previously, he was sales and marketing director at Phillips Petroleum.