Emily Taylor, Nominet's long-serving legal and policy director, has resigned.
The non-profit company in charge of the .uk domain registry declined to explain her departure.
It sent this statement: "We can confirm that Emily Taylor has resigned from Nominet. We thank Emily for her long and loyal service to company and the ccNSO and wish her well for the future."
The ccNSO is an ICANN policy body.
Taylor joined Nominet in 2000. She launched its dispute resolution service and went on to represent the UK at international internet governance meetings.
She was also company secretary, and managed Nominet's Policy Advisory Body, a part elected, part appointed group designed to give internet users outside the domain business a voice.