The lease on Transport for London's Class 378 units is due to expire in June 2027, so TfL need to decide whether they will renew the lease or source new replacement trains.
The 378's are built to special dimensions to fit the unique profile of the East London line suburban routes, where trains use the narrow single-bore Thames Tunnels.
It is likely that the 57 Class 378 'Capitalstar' trains which provide the majority of services will be retained but lease costs could increase, especially due to the special dimensions of the trains that can't be replaced easily.
A new build of a special train type would take up to four years so decisions need to be taken now. At the end of the current lease period the oldest of the train type would be 18 years on a train that is expected to last around 40 years.
QW Rail Leasing Ltd owns the 378's, then leases them to a TfL subsidiary company called Rail for London (RfL), which in turn sub-leases them to Arriva Rail London (ARL), which is the current London Overground operator.
If the new lease costs are significantly higher, TfL would have to urgently source a new supplier and find a leasing company that offers better rates than QW.
Currently 30 Class 379 trains, which are just 13 years old are sitting in storage, doing nothing because Greater Anglia decided the cost of leasing them was simply too high. Newer Class 720 and 745 trains now run the services which have been leased at much more favourable rates from companies who have now entered the leasing market.
QW Rail Leasing made a loss of £9.4million in the 2021/22 financial year. It is a joint venture between an Australian and a Japanese bank.