Type 45 destroyers are running modified Win2000 OS with a "realtime" kernel. Anyway, defence stuff takes ages to develop, test and go through "trials", so it's

Type 45 destroyers are running modified Win2000 OS with a "realtime" kernel. Anyway, defence stuff takes ages to develop, test and go through "trials", so it's quite common the customer gets stuff seven or eight years after development started. In particular, the Astute sub development programme was started in 1997, the first one was laid down in 2001, and was with the RN in 2010, although there were four years of programme delay (as there nearly always is with defence programmes).