Michael Morpurgo 
Tom »s Sausage Lion 

But it »s true,  » Tom shouted.  »It was a real lion, I know it was. »
No-one believes Tom when he says he has seen a lion – padding around the orchard with a string of sausages in its mouth! No-one, that is, except for Clare, the cleverest girl in the class. Together, she and Tom plan to prove his story is true – by catching the lion!