This decision was made official late in 1973 by the Edward Heath administration, who changed the name from Super Antelope to Chevaline.
Chevaline was devised as an answer to the improved Soviet defences around Moscow, the system being intended to increase the probability of at least one warhead penetrating the city's Anti-ballistic missile (ABM) defences, something which the Royal Navy's earlier Polaris RVs were thought to be unlikely to do.