Transition to the mark 4A warhead is ongoing to ensure that we continue to have a safe, secure and available stockpile until the replacement warhead is available by the end of the 2030s. The replacement warhead is in its early preliminary phases and will come after the transition to the upgraded mark 4A warhead. It is too early, therefore, to provide a cost estimate at this stage.
If the hon. Lady had listened to the previous answer, she would know that the current funding is being spent on transitioning to the mark 4A upgrade of the existing warhead scheme. We are engaged in the design and the process to get to the replacement warhead in nearly 20 years. Just like the rest of the nuclear deterrent budget, it is part of the overall budget. It was agreed in 2015 as part of the £31 billion for the Dreadnought programme. We continue to spend that, and I expect there to be a budget line to continue with the deterrent. As long as this Parliament votes, as it did in 2016, for that deterrent to exist, there will be a budget for it.