South Wales Police Chief Constable, Matt Jukes, will be stepping down from his position to take up a job with the Metropolitan Police in London.
Mr Jukes, who joined South Wales Police 10 years ago, will become Assistant Commissioner at the Met in November this year.
The Chief constable said "it has been a tremendous privilege" and added that the force "has made a real mark on me. There will definitely be a bit of me that is ‘Cymru am byth’ as I move on to protect another capital city.”
South Wales Police said from November 7, Deputy Chief Constable Jeremy Vaughan will be Acting Chief Constable for an interim period, and Assistant Chief Constable Jenny Gilmer will be Acting Deputy Chief Constable. Other interim positions will be announced in due course.
Mr Jukes was borough commander in the Yorkshire town of Rotherham from 2006 to 2010.
More than 1,000 children were exploited in there between 1997 and 2013, with local authorities, schools and police among agencies that failed to tackle the problem.
A report on the scandal by Professor Alexis Jay suggested that Mr Jukes’ leadership marked a point where police became more proactive in dealing with the abuse.
After serving in South Yorkshire Police, he moved to South Wales, with the police and crime commissioner there Alun Michael backing him as an outstanding leader.
Mr Jukes worked his way up to the top post in South Wales Police, becoming Chief Constable in January 2018.
He has also held national positions including in counter-terrorism and Welsh health and is chairman of Police Sport UK.
South Wales Police and Crime Commissioner Alun Michael said Mr Jukes "has led the force with great integrity, professionalism and personality."