A link might have been helpful, but I think it pretty clear that Hammond was announcing spend on the successor subs to carry the Trident missiles, currently carried by the Vanguard class subs.
The central point remains - do we need to spend billions, nevermind this 350 million, continuing with the Trident programme, a programme that is essentially a relic of the cold war "mutually assured destruction" scenarios. We are spending billions on an increasingly unlikely nuclear ICBM exhange, money that could be spent much more productively elsewhere.
In times of austerity, swords into ploughshares ought to be high on the agenda. And perhaps this govt could use some of the money to equip or latest aircraft carriers with something useful, like, you know, aircraft. Scrapping harriers and long distance sensor/scanning was a short sighted consequence of a rushed Strategic Defence Review.