This is my bread machine recipe. I set dough cycle (90mins) then allow
another 20mins, before hitting the bake cycle. The dough rises nicely up to
the rim of the pan, but the top 3" collapses - as if there was a large air
pocket under the top crust. Any ideas, TIA.

10oz strong white flour
4oz strong whole-wheat flour
250ml cold water
15ml olive oil
2 tsp fast yeast
1 tsp each of sugar and salt
Bertie