But now it is the EU that is playing chicken and they haven't realised that the game has changed.

Can you elaborate on that Nigel? As far as I can see, both sides are still playing chicken and nothing has changed in that respect. Being prepared to pay the cost of losing is part of the game. There is a list of the standard 'game theory' games here, and to mind 'Chicken' is still the best fit. Which do you think is better?

Personally, I think the game was initiated when David Davis was saying all the UK needed to do was stick to its demands and the EU would give in at the last minute, which is as textbook an example of 'chicken' as you could hope for.