BBC London 94.9 breakfast presenter Jono Coleman's leaving the station to return home to Australia.
Co-host Jo Good will take over on her own until a permanent replacement is found.
It's less than a year since Coleman launched his breakfast show on the station. He previously worked at Heart 106.2 but was dropped in favour of Jamie Theakston.
The BBC says he's moving back to Australia to care for his mother, Sylvia, who will undergo an operation in the new year.
The station's David Robey said: "It's paramount that we get the right person for BBC London and the right person to gel with Jo. Jono and Jo were beginning to make a real impact in the most competitive breakfast radio market in the UK, following in the substantial footsteps of Danny Baker, but we understand that family will always come first."
Coleman added: "Jo Good and the team have all been great during this worrying time and I wouldn't hesitate to work with any of them again."