Here is a sample of his work:
And he has illustrated Beatrix Potter., according to this story.
A previously unknown Beatrix Potter story, "The Tale of Kitty Boots," was discovered in the Victoria & Albert archive in London. The story will be published for the first time this fall  with illustrations by Quentin Blake. Two years ago, Penguin publisher Jo Hanks found mention of the unedited story in a 1914 letter, which set her on a research quest.
Here is more detail, from the same source I think:
“The Tale of Kitty-in-Boots, a manuscript by Beatrix Potter, was rediscovered ... when Jo Hanks, publisher at PRH Children’s in the U.K., stumbled across an out-of-print literary history about Beatrix Potter from the early 1970s. Hanks found in the book both a reference to a letter that Potter had sent her publisher in 1914, which referred to a story about ‘a well-behaved prime black Kitty cat, who leads rather a double life,’ and an unedited manuscript of the tale. A trip to the V&A archive, where many of Potter’s items are kept, revealed three manuscripts, handwritten in children’s school notebooks, one rough colour sketch of Kitty-in-Boots, a dummy book with some of the typeset manuscript laid out and a pencil rough of arch-villain Mr. Tod.”
Another Blake cat:
And here's a bunch more.