New Trident? But you have not used the last one we bought you!

The current defence review has come about because of the Austerity measures needed to cut the Sovereign debt of the country. Cause and effect.
One of the decisions to be made is about Trident. Do we extend its lifespan or replace it? Those seem to be the options, but what about keep them as they are. Why replace or upgrade them? They have not been used. They are not out of date (no star wars system has yet been developed that can stop them!). The replacement costs will go to America not the UK and they are still good until 2024 (that is 14 years away).
To me this is a no brainer.
We have no enemies that we can use these missiles on. Russia is our friend, China may become a threat but the current Tridents are more than enough to hold the status quo.
Each Trident missile has a range of up to 7,500 miles (12,000km) and is accurate to within a few feet. Their destructive power is estimated as the equivalent of eight Hiroshimas.
The UK deploys 16 Trident missiles on each of its four Vanguard-class submarines, of which one is on patrol at all times. The fleet is based at Faslane in Scotland.
More than enough fire power!
In my opinion we don’t need another.This ones still ok! 20 billion saved!