Did you know that the Lib Dems are offering that they will hold a "full defence review" including Trident, but have already committed to not replacing it fully?Additionally, their offer of fitting nuclear warheads to cruise missiles on board Astute submarines is rubbish. The Astute's cruise missile, the Tomahawk, has a range of 1,500 miles and maximum speed of around 550 mph. It would take over 2.5 hours to travel from the Mediterranean to Iran, which is about as far as it can go. You could overtake it with Thomas Cook holiday plane and shoot it down with a spud gun.
The existing Trident II missile has a range of 7,000 miles and a maximum speed of over 13,000 mph. It can travel from the South Atlantic to North Korea in 18 minutes and deliver several nuclear warheads at once.
The two systems are a million miles apart.