Boris Johnson’s partner Carrie Symonds has made her first public speech since moving into Downing Street last month.
She gave a short address to the Birdfair environmental event at Rutland Water Nature Reserve.
Ms Symonds is also due to join a question and answer session with Chris Packham, presenter of BBC Springwatch.
She quit as director of communications for the Conservatives last year and is now a senior adviser for US environmental campaign group Oceana.
The 31-year-old works with the charity’s marketing operation in London and a profile on its website describes her as being “passionate about protecting the oceans and marine life”.
More than 24,000 people attended Birdfair last year over three days.
Tim Appleton, founder of the annual event for birdwatchers, said it has raised £40m for global conservation projects in the 31 years that it has been running.
He said: “We’re absolutely over the moon that Carrie is supporting us and we hope she will continue supporting us and conservation for many years to come.”