Firstly, thank you for your reply and sorry for taking so long to get back to you.
I’m a novice at this and it took ages to get the PHP error log configured.
Having got it sorted (I think), the PHP error log is still empty after the error occurs. I’m pretty sure that I’ve got the log configured properly as the ‘PHP Error Log’ plugin manages to locate it and doesn’t report any inconsistent read/write permissions.
The full error message is as follows:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, root@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.