You can think of your variables, your moving pieces, as being moved back and forth on a set of old-fashioned scales until everything is in balance. If one moves across to this side, another one has to move that way to compensate. In a sense, these are everyone’s wants and desires being balanced against each other until everyone is satisfied that the deal is fair. Bit like the scales of justice.

Once everything is perfectly positioned, you can shake hands, sign on the dotted line, and it’s a done deal. But you do have to be sure that all the movable pieces stay flexible before you sign off on the deal.

If you agree a firm price in exchange for an extended deadline, before you’ve completed discussions, you’ve glued down those two weights in your scales. So when they ask for something else, you can no longer say ‘Yes, but it will cost you … ’, because you’ve confirmed the price. That was silly of you, wasn’t it? So don’t agree anything firmly until you’ve got the whole deal in place. Just say, ‘That price could be possible. Let’s put it on one side for the moment while we discuss delivery.’

And here’s another thing to look out for. Suppose you reach an agreement, shake on it, and then your client says, ‘By the way, we’d like to extend our payment time from thirty days to sixty.’ Or your child says, ‘Now we’ve sorted out bedtime, can I also have my phone in my room? All my friends are allowed to … ’.¹⁸

Dammit! You could have made that one of the moving pieces, only you’ve gone and agreed the deal already. You have nothing left to trade with because you’ve used up all the variables that matter.

People can be slippery, especially when they want something they’re not sure they’re going to get. And any canny negotiator knows that it can be a good idea to keep something up their sleeve. You can’t ask them to make any more concessions now, because you’ve agreed the terms, so you have no bargaining chips left. You either agree to their extended payment time – or whatever – or you lose the whole deal. They are well aware of this, however disingenuously they might make out that this is a whole separate matter. Of course it isn’t. It’s just an issue they didn’t want to bring into the main negotiation because they didn’t want to have to give any ground on it.

The way to prevent this is to ask, before you fix the deal in stone, whether there’s anything else they want to discuss, include, alter, agree, rearrange. If they say no, they’re on the back foot if they try to introduce it later because you can say, ‘No, we agreed there weren’t any other points to cover. That’s the deal as it stands.’ They really can’t argue with that so long as you’ve made it quite clear. And if they ever negotiate with you again, they’ll know not to try it on with you.