The following was taken from a 2016 edition of Tax Adviser:
For years the Caillebotte v Quinn logic  50 TC 222, ruled, and applied the wholly and exclusively logic to self-employed taxpayers who ate and drank in the course of their self-employment.
The Caillebotte logic specifically covered a building contractor’s daily lunchtime sandwich, so advisers were still struggling with an evening meal.
In 2009, the ITTOIA legislation was modified with the insertion of s 57A, which codified and slightly ameliorated the harsh logic of the Caillebotte decision and now specifically allows for subsistence costs (reasonable expenses on food and drink), where travel is occasional and outside of normal travel patterns, or for itinerant trades.
So, the courts have generally accepted that if travel is allowable, the reasonable food costs say for evening eating is also allowable (see also BIM47705).
This effectively tells us that if Stuart is struggling to get a deduction for his travel, then he will also struggle with his subsistence costs, and even if the circumstances were such that he could claim travel and subsistence costs, travelling and staying with Jean raises the spectre of duality of purpose (the pleasure of her company in the same B&B) and even whether they could both claim tax relief for effectively the same travel.
We are always surprised by how diversely deductibility of subsistence costs is interpreted by practitioners and we regularly hear at conferences for example, that some advisers will allow alcohol and some will not – perhaps the Temperance movement has come to tax.
Certainly we cannot find any legislative suggestion that alcohol is a pleasure and therefore next to sin and therefore taxable. So have a drink on the Chancellor (see also BIM47705)!
We also wonder if in the name of simplicity sole traders should be allowed to have flat rate deductions for food and drink that are available for employees.
So, we cannot but conclude that in the absence of an effort to redraft the legislation in clearer terms for the self-employed, the rules will remain a box of sundered fragments.