The Covid-19 pandemic has pushed back the re-opening of Island Line by around six weeks.
The suppliers of the reconditioned rolling stock, Vivarail, have been particularly affected by the pandemic as the number of engineers able to work on trains at any one time significantly reduced and the supplier of the traction system was unable to work at full capacity.
Other problems include teams required to form work bubbles and having to ensure sites are Covid secure.
South Western Railways now aim to have the first trains running in mid-May. In the meantime a replacement bus service will continue to operate.