Sir David Attenborough has confessed to being a little nervous before filming a documentary with the Queen in Buckingham Palace's gardens - because of concerns about noisy traffic.
However, the veteran broadcaster's worries were unfounded as the Queen - who he praised as "very gracious" - took it all in her stride and even joked about a loud aircraft.
The leading figures will appear in the ITV documentary The Queen's Green Planet being screened next week and were filmed last summer strolling in the palace gardens chatting about the many trees in the open space.
Interviewed for the latest edition of the Radio Times, Sir David said: "Yes, there was a certain amount of apprehension because all sorts of things could have gone wrong.
"There were problems in that where the palace is, geographically, there are always police sirens and ambulance sirens that make filming difficult. But she took it all in her stride.
"It was a privilege of course, a very nice occasion -- and she was very gracious."
During the programme, due to be screened next Monday, the Queen jokingly attributes a loud aircraft to the US president or possibly his predecessor saying: "Sounds like President Trump, or President Obama."
Sir David and the Queen share a strong rapport during their chat and have known each other for a long time, with the broadcaster producing the Queen's televised Christmas Day address for more than five years in the 1980s and 1990s.
Asked about their on-screen chemistry, he added: "She is very un-solemn, very good at putting people at their ease."
The Queen is known for her sense of humour, which she uses to calm the nerves of nervous guests with a comment or amusing question.
The documentary examines the Queen's Commonwealth Canopy, a project to create a network of protected Commonwealth forests around the globe in tribute to the Queen's service to the family of nations.
Sir David highlighted her deeply-held passion for the Commonwealth: "She certainly cares for the Commonwealth and she very clearly cares for the natural world. What this project does is to ensure the future."
The Queen's Green Planet will be screened on ITV at 9pm on Monday April 16.