In London's legal quarter, there are several large private courtyards and grassed areas, open to the public for limited times during the day, usually around lunchtime. Here's one of those that subtly re-enforces that legal sense that access is not a right but is permissive. So to add to the more usual message of "Please keep off the grass" which in most cases is usually sufficient, this is re-enforces that legal-ease closure message for the lawn.
