The Shadow of the Great Fire - Wendy Leighton-Porter

The seventeenth book in the Shadows of the Past series:

In 1666, as London recovers from a deadly plague, the old medieval city with its narrow streets has become a tinderbox. After a long, hot summer, a small spark is all it takes for the whole place to go up in flames - but is this a simple accident or a deliberate act of sabotage?

Towards the end of August, only days before the Great Fire will break out, three time-travelling children and their talking cat land on the doorstep of one of the most famous figures of the 17^th century. Can they discover why they've been sent there before it's too late? Time is running out...