They say: 'Our research says we need X trains per hour. Here are the trains. Go run it and we'll pay you Y'.
The downside is that TfL (and London tax payers) carry the RISK. If they need MORE trains, then it's TfL who'll have to pay
DfT are the UK Association of Chicken Shops. Everyone is selling chicken and paying their fees, but has different ideas on how to do it.
1) People who understand railways run them
2) Their employers funnel investment back into the railways
3) The above has been happening, without interruption, for at least ten years.
Meet those rules and we can have all the fucking BahnCards we want!
Unless Chris Grayling or Andy McDonald suddenly learn how to fart out spare passenger capacity, ideology won't fix them. WHATEVER way your politics fall.
Better Knowledge and logistics will.