The Chief Constable of Lincolnshire Police has announced he will step down from the role next year.
Chris Haward said on Monday that he was leaving the force to take up a new job with the National Police Chiefs' Council (NPCC).
He said the decision to move on after three years at the helm has been "unexpected" and "immensely difficult".
He will leave his role in February and become the NPCC's UK coordinator, tackling serious and organised crime.
"I did not expect to be leaving Lincolnshire at this point, but an unexpected opportunity has arisen and it's time for a new challenge," he said.
"I'm really proud to have served as Chief Constable in Lincolnshire Police and of the people who serve in this force."
Lincolnshire's Police and Crime Commissioner Marc Jones said Mr Haward had been a "dedicated" and "hardworking" police chief who had "worked tirelessly to create a police force equipped to tackle modern crime and to keep our communities safe".
Before joining Lincolnshire Police in December 2020, Mr Haward was head of the East Midlands Special Operations Unit.