he big elephant is the statement made in 06 that it would take 17 years to field and the extant system would be out of service in the early 2020s. Why didn't they do anything about it then before it was too late - especially considering the statement that life extensions were unlikely to be effective or for particularly long. We now have fewer that 10 years to decide upon a system and get it into service.
they have done something. About £1B has been spent since the paper in various lead-in design and pre-production contracts. You can find details if you google it - they just haven't made a song and dance about it.
e.g.........
Defence secretary publishes update on progress with Trident replacement | Nuclear Information Service
See pages 19-21....
http://researchbriefings.files.parli...26/SN06526.pdf