After reading a letter from a Croxley Green school pupil, the ambassador for Costa Rica decided to visit his class to answer the questions in person.

William Gross wrote to the embassy in London while carrying out research for a geography project on the Central American country.

On receiving the message, ambassador Pilar Saborio decided to visit York House School to give a talk on the country she represents.

William asked two questions: Why doesn't Costa Rica have an army and why is it important for the world to be less polluted?

The ten-year-old, whose favourite lesson is chemistry and wants to be a scientist or a hedge-fund manager when he grows up, said: “I was quite excited and felt very honoured when I heard she was coming to see us.”

Headteacher Peter MacDougall said: “My secretary told me the ambassador from Costa Rica had called and I said 'don't be so ridiculous'.

“I rang the ambassador's office and spoke to her secretary and she said she was really excited about coming.

“She rang my office and spoke to me and William, but said she would rather answer his questions in person.

“She seemed really fired up and excited about it and it's a very exciting thing to happen for us. It's not the kind of thing that happens every week, I'm thrilled.”

Costa Rica ranks first in the Happy Planet list (in the most recent list, the United Kingdom was 74th) and is the greenest country in the world. It has roughly the same population as Scotland but has less land.

It was named “the rich coast” by Christopher Columbus after he visited and saw the long beaches, luscious jungle gold jewellery of its people.

Ms Saborio represents Costa Rica in the United Kingdom and said her job is made easier by the fact that the two countries agree on most things.

She added: “It was a very well structured and polite letter with fantastic handwriting - better than mine.”