My tortoise is not eating - is it too early for him to hibernate?

by Karen
(London)

We have begun to look after a tortoise that we took in when a friend moved abroad. We believe he is quite old and has always lived outside. He ate well during the summer months, but over the last few weeks has hardly eaten anything. We understand that as the climate cools he will not be as active, but we are worried that he will die if he does not start eating. Can anyone tell us if they think it may be because he is ready to hibernate? Or is it too early? Do we need to bring him inside with a warm lamp until it's hibernation time now that the climate is cooling?