Most well-known for his work with children's author Roald Dahl, Blake has illustrated more than 250 books by different authors and turned his attention to large-scale works.

At the age of 85, he has slowed his schedule but has definitely not put down his pencil.

"I draw every day, yes, if I possibly can," he told AFP at the sidelines of an auction of literary classics with illustrated covers.

Dressed in white trainers and with bushy eyebrows and a mischievous look, Blake resembles one of his famous characters.

Matilda, the BFG and the Twits are just some of Dahl's creations brought to life by the illustrator.

Ahead of a new exhibition at London's House of Illustration of Blake's rarely-seen nudes, he said he still cannot pinpoint the secret of his success.

"It is hard for me to say. It always comes (as) a little bit of a surprise to me," said Blake. 

- 'Carefully planned' drawings -

Born in Sidcup, south-east of London, he first began drawing around the age of six. 

After a childhood interrupted by World War II saw him evacuated to the English countryside, he returned home in 1943 and soon had his drawings published in the school magazine.

The budding young artist earned his first fee at the age of 16, when his cartoon was published by Punch magazine, and he continued to draw while studying literature at Cambridge.

During the following decades, Blake taught at London's Royal College of Art, curated exhibitions at institutions including the National Gallery, while continuing to inspire children with his drawings.

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"They seem to like them," he said modestly, although noting people are often unaware of the level of preparation which goes into his work.

"In fact they are very carefully planned, the whole book is organized, but they appear to be spontaneous and so in a sense they have very sort of direct reactions," he said. 

Blake, who has visited schools across England and France, advises children to "start drawing and draw a lot".

"Inspiration is a funny thing... You find your imagination working but you can't turn it on, you just have to start drawing," he said.

- 'Loved by generations' -

Blake's vast collection of original illustrations -- 35,000 works in total -- are kept at the House of Illustration which he founded in 2014.

His drawings are filled with a sense of humanity, humor and enthusiasm for life, according to the centre's director Colin McKenzie.

"I think he is a wonderful illustrator, there is a fluidity to his work that is just unique," he told AFP.

The upcoming exhibition of Blake's work will feature pencil drawings of women and cupid's arrow and will open on February 14, Valentine's Day.

Blake describes illustration as an art form which is often overlooked, despite there being a "great tradition" in his home country and across the Channel.

His enthusiasm for French culture has seen the illustrator included in the South Ken Kids Festival, organized by the French Institute in London.

"He has a love of French culture. He's a true francophile," said festival director Lucie Campos.

"He's a person loved by generations of readers."