Contract law - practical benefits vs legal benefits

Don't look at this in terms of "practical" and "legal benefits", its a rather silly dichotomy. People made up the term "legal benefits" to try and rationalise Roffey, but its not helpful. Its an example of over-zeaulous text-book writers making **** up to try and simplify things for their students, but actually just confusing them.

The word "legal benefit" simply means something that counts as consideration. This definition is entirely circular: the term "legal benefit" doesn't actually mean anything. This is probably why you are getting confused, because you are trying to rationalise a dichotomy between "practical benefits" and "legal benefits" which is not actually rational in the first place. I could go on for ages about it, but I'll stop there.

All people are referring to when they say "legal benefit" is the general rules on consideration: that is rules like you can't have past consideration and so on.

The effect of Roffey is that it widens what counts as consideration in the case of an increasing pact, that is where one agrees to pay for for what he is already contractually entitled to receive only.

I think it is more sensible in your notes and in exam questions to rationalise it as follows.

The basic rule is very very simple: you need to have consideration to form or to vary a contract. Roffey doesn't alter this, and this is what all the cases say.

What the cases do is help you decide whether there is consideration or not. They give you various rules to help you decide whether there is consideration in a variety of different circumstances. But the point is that they aren't seperate rules of law in of themselves, they are just saying whether there is consideration or not. For instance, in the case of past consideration, the general rule is that giving consideration for something that has already been done does not count, unless there was an understanding that the party undergoing a detriment would later be compensated for it: Lord Scarman in Pao On.

All that Roffey does is widen the scope of consideration in increasing pact cases. Its still consideration, and you still need consideration for the contract to be varied. The fact that some academics have made up a dichotomy between "practical" and "legal" benefits doesn't change the essential point, and this dichotomy is not referred to in the cases.
What I'm trying to say, is that Roffey doesn't do anything to Stilk. Roffey approves Stilk: Stilk says that consideration can't derive from an existing contractual obligation. What Roffey does is that it finds away around Stilk: in Roffey, Roffey agreed to pay more not to increase his strict legal rights, but to obtain a practical benefit - you still need consideration.
(this is what people mean by the difference between "PBs" and "LBs", but I still think its a horrifically confusing way of looking at the decision, it misunderstands it: of course if someone wants to contract to obtain a "PB" they should be able to do so, people do that all the time, that is what Roffey is saying. I would completely ignore the dichotomy and concentrate on what the actual rules on consideration are and whether they are justifiable, rather than trying to artificially pigeon-hole them in a way that is neither rational nor appears in the cases).

All that Re Selectmove says is that you can't apply the wider concept of "practical benefit" to decreasing pact cases (where one agrees to receive less than what he is entitled to), because the Court of Appeal felt bound by the early authorities of Pinnel's Case and Foakes v Beer: all this means is that you apply the regular rules on consideration, and you don't apply Roffey, in this kind of cases. Whether this is consistent, and what the House of Lords would do to Roffey and Foakes v Beer in such a case went to the HoL, remains to be seen.

Hope that makes sense...

If you are confused about this, read O'Sullivan's article "in defence of Foakes v Beer" in the CLJ.