Elmlea, Stuff, STH
We have been around this particular buoy a few times before. JSP 752 has now been amended to remove the specific exemption on recepts for items up to £5, however it still recognises that there are situations where it is not practicable to obtain a receipt. It is rather vague, possibly to allow the auditor some discretion (since auditors are recquired to "interpret these regulations reasonably"). I am not an auditor, but if I were, I would think your un-receipted burger to be a reasonable claim in the circumstances, so long as you did not take it to extremes.
By the way, JSP 752 places no definition on what constitutes a valid "receipt" and what does not, so again it is left to the auditor's discretion. This may not sound very helpful, but actually allows a multitude of flexibilities if the auditor is "reasonable". Don't you just love those legal people!
Regards
Ginseng