It’s not often you hear the Queen in conversation at all, let alone with a member of broadcasting royalty like Sir David Attenborough.
Sometimes, you might catch a few seconds of her in discussion at an event, but never has the Queen been recorded talking for 90 minutes in the grounds of Buckingham Palace.
The conversation between the two nonagenarians, recorded for an ITV documentary, The Queen's Green Planet, reveals some real nuggets of information.
The Queen discusses climate change, Donald Trump, and even her own demise.
And we get a closer look than ever before at the Queen’s sense of humour.
That humour is often written about and referred to by Palace courtiers but rarely is it seen in public.
The Queen and Sir David chuckle over a forlorn-looking tree which the Queen suggested had been "sat on" at a garden party and she makes a sideways comment about the decision to "stop children playing conkers" because of "health and safety".
When the broadcaster, known for his series like ‘Blue Planet’ and ‘Planet Earth’, pointed out that a sundial had been positioned in the shade, the Queen laughs and says: "Had we thought of that? That it was planted in the shade, it wasn’t in the shade originally, I’m sure?"
She adds: "Maybe we could move it?"
Overall, it’s a very watchable discussion between two people in their nineties who are well known all over the world for vastly different reasons.
The programme is based on a project called The Queen’s Commonwealth Canopy, a plan to create a network of forest conservation projects dedicated to the Queen in all 53 countries of the Commonwealth.
Prince Charles, as well as Princes William and Harry, have all been helping to promote the canopy scheme across the world from the Caribbean to Canada and from Australia to Africa.
The programme also follows film-maker and campaigner Angelina Jolie, who helped with the canopy project in Namibia – where one of her children was born.
The Queen even tells Sir David she hopes the project to plant more trees may even have an impact on climate change.
"So, if all countries continue to plant, it might change the climate again," she tells him.
Which is an interesting observation given a joke she makes elsewhere in the film about the US president – someone who has said he does not believe in the science behind climate change.
As the pair chat in the garden, a helicopter flies overhead, and the Queen asks: "Why do they always go round and round when you want to talk?"
And then then she jokes: "Sounds like President Trump."
When Sir David suggests climate change might lead to "all kinds of different trees growing here in another 50 years" the Queen jokes, "It might easily be, yes. I won’t be here though."
The UK’s Commonwealth Canopy forests are in Epping near London, the National Forest in central England and Wentwood Forest in Wales.
The Queen and Sir David were born just three weeks apart and were both 91 when the cameras recorded the stroll around the gardens last summer.
As for the sundial? I’m told by the Palace’s Head Gardener that is has now been re-positioned into the sun.
Sir David will be relieved.
The Queen's Green Planet will be broadcast on ITV at 9pm on Monday 16 April