In my Security Sales days I was asked to design a routine to ensure that a client's clean desk policy WOULD be implemented.
In the first week we had the night guards walk round each office and leave a pre-printed, polite notice stating that the company had a clear desk policy and would the occupant of the desk on which the note had been left please ensure they cleared their desk and locked it before going home.
In the second week the note carried the added threat of "disciplinary action" for non compliance.
In the third week we simply swept every thing from the desk top into individual bin liners and took it to the gatehouse, leaving a post-it note saying where they might attend to reclaim their possessions.
In the fourth week we threw everything into one dustbin and delivered it to the MDs Sec so that she could sort out anything that belonged to the company and bin the rest.
In the fifth week 7 people handed in their notice.
The MD was unrepentant and implemented a hot desk policy which I suspect had been his intention all along.