Question to the Ministry of Defence:

To ask Her Majesty’s Government what is the in-service date for the UK Trident Mark 4A nuclear warhead; what are the estimated costs of the Mark 4A programme; and what progress has been made to date in delivering that programme.

I am withholding details of the date of the Mk 4A's component's entry into service, progress to date and the cost of the programme, for the purpose of safeguarding national security.