Excellent drainage can only do so much. It won't make much difference in consistent torrential downpours. They have a set limit of how much rain they can cope with per hour. I think the Lord's drainage is something like 30mm of rain per hour (or some figure like that, anyone find it?). As for OT, well the Lancashire board are planning to put their own system in for next year.
I think Lord's spent ?1.25M on drainage.