Ancient Rome Refocused
If I was going to do walking tour of Great Britain I would pack this book with an extra pair of socks.
It’s a great book, based on a series of lectures given at Oxford University. The book is filled with maps and drawings and insights into the ancient world.
Check out the great map on the inside cover. Go for an old edition. It has a lot more dash. It's relatively small, and easy to put in
An interesting tidbit is that according to Collingwood there was a lot more diversity in Romano Britain that discussed in the modern discourse of today. Considering Collingwood lived during the time of the British Raj, I tend to believe his conclusions.
If you intend to visit Romano Britain, this is the book. Just make sure there isn't a updated version out there. You may want to bump a modern map up against it.