"Dear Sir David, Can you tell us why eagles are called birds of prey? Yours Sincerely, Year 7, Marshland High."

Curious students decided to go straight to the nation's best-known naturalist with a query about birds.

Cambs Times: Marshland High School teacher Ellen Castley and pupil Alfie Baxter with the letter from Sir David AttenboroughMarshland High School teacher Ellen Castley and pupil Alfie Baxter with the letter from Sir David Attenborough (Image: Ian Burt Photography)

And you could have knocked them down with a feather a few days later when they received a handwritten reply from Sir David Attenborough himself.

Year 7 science students from Marshland High School, near Wisbech, wrote to the legendary broadcaster at his home in Surrey asking why birds which use their talons to catch their food are known as birds of prey, rather than birds of predator.

Cambs Times: Sir David's letter to Year 7 science students at Marshland High SchoolSir David's letter to Year 7 science students at Marshland High School (Image: Ian Burt Photography)

Sir David reached for his pen and replied: "Dear Form 7XI, Eagles 'prey' on smaller mammals, who are also called their 'prey. Predators is a noun meaning, roughly, hunters. So 'birds of hunters' makes no sense; 'birds of prey' is very accurate - and shorter. Best wishes, David Attenborough.”

Teacher Ellen Castley said: "The class is overjoyed, as am I, that he replied. I can't stop telling everyone.”

Cambs Times: Marshland High School pupil Alfie Baxter, 12, with the letter from Sir David AttenboroughMarshland High School pupil Alfie Baxter, 12, with the letter from Sir David Attenborough (Image: Ian Burt Photography)

Sir David, now 95, began broadcasting in the 1950s, when one of his first colour documentaries featured a golden eagle.

Since then he has made numerous programmes covering all aspects of the natural world, with some of his most famous being Life on Earth and The Blue Planet. This year saw the BBC broadcast his most recent series, A Perfect Planet.

Cambs Times: David Attenborough on a visit to Cley Marshes in Norfolk in 2014David Attenborough on a visit to Cley Marshes in Norfolk in 2014 (Image: AndiSapeyCopyRight2014)

Although best known for his programmes about the animal kingdom, in 1998 Sir David made a 10-part series called The Life of Birds.

While his early work focussed on the natural world, he has in recent years turned to supporting environmental causes such as restoring diversity and highlighting the amount of plastic which finds its way into our oceans and its impact on marine life.

In an interview with the BBC, he said: "The world is waking up to what we've done to the planet."