"If you move from 20 different ways of doing something to one, that reduces the risk of something going wrong enormously. Then you make sure that the process around that makes sense, end to end: making sure it isn’t convoluted and complex. You put in all your controls, both preventive, and detective. You try and make as many of them automated as possible, and then you test them constantly to make sure they’re working. That is the deeply unsexy but very important work we have been doing"