South Wales Police's top officer is moving to take up a top post at the Metropolitan Police.
Matt Jukes is to be made assistant commissioner, starting work in November.
He was made Chief Constable of the Wales' largest police force in January 2018, and has held national positions including in counter-terrorism and Welsh health, and is chairman of Police Sport UK.
The announcement was made on Tuesday, with the Chief Constable saying: "I joined South Wales Police ten years ago and I have never looked back.
"It has been a tremendous privilege to hold senior leadership positions in the Force; since 2013 as Deputy Chief Constable and then, from 2018 as Chief Constable. In that time, I have seen so often the care and compassion of colleagues, and the strength of the South Wales Police family.
“Working with colleagues in South Wales and with our communities has been tremendously rewarding. Despite the many challenges we have faced together, our people have proved themselves to be capable of keeping local communities safe and policing major international events.
“And South Wales Police 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 and to keeping London safe.”
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 also lead Rotherham during part of the sex abuse scandal when he was borough commander in the Yorkshire town from 2006 to 2010.
More than 1,000 children were exploited in Rotherham 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 Michael said: "Matt Jukes has been an outstanding leader of South Wales Police and I want to thank him warmly for the significant developments that we have seen during his time at the helm and the positive direction in which the force is heading.
"In so many areas of activity, South Wales Police is a beacon force which is a credit and a reflection of Matt’s leadership and strength of the chief officer that he has built around him.
“When I appointed Matt as Chief Constable, I knew we had the right person to lead us on through some very difficult financial challenges and the team has continued to evolve and adapt in order to face and embrace new challenges. He has led the force with great integrity, professionalism and personality and has shown a strong personal commitment to the communities of South Wales and in supporting the officers and staff who work tirelessly to keep us safe and confident."
He added they would move "quickly" to attract applications for the job.