This may be true. But if so, what precisely is the unsatisfied condition? Perhaps there is an implied term of some sort, and in this context I note Allan's proviso:

but the cards are sold to enable holders to access ET's account/property for communications and not adventitious gain

This was not, as I understand it, an express condition of the contract of sale. At least under English contract law, neither (it seems to me) does it meet the requirements of an implied condition or term. That being so, where is the (legal) wrong? It is not wrong for D to take advantage of another's bad bargain, especially when D has played no part in setting the terms of that bargain.

Indeed, and by way of aside, D's role may, in law-and-economic terms, be efficient: D acts effectively as an arbitrageur. So there may not even be a non-legal wrong. But either way, it seems unattractive for the law to interfere in an arms-length contract of exchange where there is no active misconduct by D in the formulation of the bargain. If an analogy with mistakes may be forgiven (and it is only analogy, introduced for its possible illustrative benefit), D performs its side of the bargain to the letter: P's miscalculation is a unilateral error that goes to the background motive or calculation, not to the terms of the bargain.

Back to the election. And to the claret. Not necessarily, of course, in that order.

Regards
Andrew

ps. By the way: Lionel, on your point re ownership of the coins in the coin machine, in the wake of the HL decision in Hinks it is now clear that even the act of acquiring ownership is - in England - the actus reus of theft. Provided it is dishonest, it *is* theft. All second-hand-car salesmen, and anyone taking scrupulous advantage of the caveat emptor rule, should be very worried indeed. Of course, I haven't asked Craig Rotherham what he thinks of it all. But the next time he buys a mispriced port off the Fellows' wine list....