Nothing to do with cold feet, and everything to do with Driver training.
The 'finished product' requires far more drivers than were supposed to be handed over at the end of FCC's franchise, and the company had to recruit heavily to even get to that level.
Existing Thameslink drivers need training on the new London Bridge layout. Bedford drivers need to re-learn to East Croydon via New Cross Gate as they haven't been over it for four years.
Drivers staying at Bedford need to learn South Croydon to East Grinstead.
Drivers who are going to be based at Luton are learning to Rainham.
Drivers based at Peterborough are learning to Horsham.
Horsham drivers are learning to Peterborough, with the added restriction that they are needed for Southern duties until their transfer to Thameslink in May.
Brighton drivers are learning to Cambridge, plus they need to learn the new layout at London Bridge as mentioned earlier.
Half of Cambridge need to learn to Brighton.
*The other half of Cambridge will need to learn to Maidstone East.
*Welwyn Garden City needs a traincrew depot building. Drivers who'll be Thameslink, based there, will need to learn to Maidstone East and Sevenoaks. Most of them will need to be trained on class 700s as they haven't been yet.
*Hornsey Thameslink drivers will need route training and class 700 traction training. Hornsey needs a traincrew depot building.
All remaining GN Welwyn and Hornsey drivers will need class 717 traction training.
*Orpington Thameslink drivers will need to learn to Welwyn Garden City.
*Ashford will need to be opened as a traincrew depot, which will need a building sourced for this. I don't know if this is planned to be a new one or use/sharing of an existing one. Ashford drivers will need route training Ashford to Cambridge.
Any route knowledge I've mentioned may also require diversionary routes to be learned as well.
The items marked with asterisks * have been put back 6 to 12 months than originally envisaged. Whilst it is indeed sensible to ramp up the service in the peak from 20tph to 22tph, and then 24tph, to allow the increased flow of trains to bed in, I believe it is really the Herculean logistical task of training that has been realised as the limiting factor.
In the above examples of route learning needing to be done, most involve travelling a fair distance before reaching the route required to be learned, and all involve avoiding travelling with newly qualified drivers, or drivers who have recently had an incident, as they aren't allowed anyone in the cab with them. Avoiding the cabs being too full of route learners is another thing to take into account, and add to that few trains running through London Bridge currently.
Previously, there has been a great deal of training up until this point also: all existing Thameslink drivers were trained on class 700s; most GN drivers trained on class 387s, and a fair amount of GN drivers on class 700s.
A number of Driver Instructors/Trainers have needed training up.
In the future, as well as all the above, ATO training will need to take place.
This has been, and will continue to be, a HUGE task. I think the 'finished product' will run okay mostly - better than most people's predictions, but in the short to medium term, the resourcing of a driver with the requisite route knowledge, or the swapping of drivers half way with the potential for delays to knock-on, will be the likely cause of problems.
