I found these children's books in an antique store, here in Springfield, Mike's Unique. I bought them for my nephew's one year old son. He loves books with colorful pages and I like retro cartoon-related merchandise. The book based on Gerry and Sylvia Anderson's Fireball XL5 is part of the Little Golden Book series. Random House reprints many of the titles. Here is their website (and you can download an animated Poky Little Puppy for your computer). They obviously new the audience for a Fireball XL5 book might be kind of nerdy, so on the back there is a promotion for a series of Little Golden Science books.
The other book is by Whitman Publishing and is about King Leonardo. I should point out that even though Tudor the Turtle is on the back cover, he appears no where in the book.
Yes, you greatest fear has come true folks. Desdinova has become an old softy. As much as I hate to quote former President George H. Bush, you are seeing a "kinder, gentler" Desdinova.