I was not ready to TT DD when she was 20 months old. Not that i didnt think it was a good idea but just that the timing for me was not that great. Well, i nearly fell over one day when DD came up to me and told me she needed to go to the toilet - and went. It turned out the child care centre had been encouraging all the kids to go to the toilet etc and it just clicked with her.
Have not had an accident since! I dont think that it will be that easy when i try to TT her at night.