The unit and traincrew diagrams to replace 350/2 are really complex. The railway is essentially moving from a Northampton and Crewe based one to a Bletchley based railway. In time that comes with all sorts of benefits but in the interim, the rollout is complex and full of nasty surprises. I’ve been involved in more new trains rollouts than I care to remember, and I think the 730/2 is the most complex I’ve ever had the misfortune to be involved with.In all fairness, the 805/807 fleet needed far less testing (the 805 didn't even need a proper braking test), which helped them enter service after only 5 years rather than 6 (730/0) or nearly 8 (730/2) years. The main hurdle at the moment is driver training, since I am lead to understand that traincrew(?) diagrams on the future 730/2 services are quite complex. The 730/0s were rolled out at a rate of about one a week once they started appearing on the cross city line.
For an operator that usually flies under the radar, especially at the London end, it’s a fascinating jigsaw to get it to all work in the right time.