Blossom - you are of course quite right. Ring fence the issue without fear of anything. Rather then pussyfooting around.
To lighten this up slightly. I work for a large FTSE company. Expenses are always a hot topic. So the company sends blanket emails to all saying you are spending too much or the rules aren't being followed I.e no 1st class rail travel.
Blooming well look at the highest spenders, we have to claim line by line. Then write and address those people, otherwise it's pointless.