[eluser]ray73864[/eluser]
ok, i have set the log level and run the tail command. I then refreshed the home page to get a log entry, went into the admin section and altered the page then clicked save, then refreshed the home page, then altered the page again and refreshed the home page.
the logfile has things like 'file written: frontendNavigation, but it only ever retrieves a page, it never seems to write a new page cache.