Second or First Strike Cooperation
The light blue footprint reflects the limitations of the UK's Trident II D5 SLBM coverage, from the Atlantic Ocean launch basin. Half of Russia, most of China, and all of North Korea are not in the (likely 8,000-12,000 km) UK Trident range. This means the UK very much needs to launch in cooperation with the US, assuming US assumed global coverage (especially from the Pacific Ocean).
If France's newish M51 SLBMs (at 8,000-10,000 km) have a 2,000 km shorter range - then that restricts France's deterrent reach even more. But then again France's deterrent is mainly to make Russia's losses unacceptable. (Map-Diagram courtesy FAS, UK Defence Review via BBC, 2016).
UK Trident Vote
On Monday night, July 18, 2016, a majority of UK Members of Parliament (in the House of Commons) voted to replace the 4 Vanguard class (Trident firing) SSBNs with the 4 new (Trident firing) Successor class SSBNs. 472 (including 322 Conservative) voted to replace versus 117. This represents more than 80% in favour - a sound mandate to replace Trident.
While it was not a surprise that most MPs voted for the replacement - because most MPs in the Commons are of the ruling Conservative Party - it was a surprise that a majority of Labour Party MPs voted for the replacement. 140 of Labour's 230 MPs voted for replacement (a total of 47 Labour members voted against replacement, while others abstained).
This Labour Party result represents a divisive thrashing of the Labour Party Leader's authority. Labour Party Leader Jeremy Corbyn is a very leftwing pacifist, so having most of his party in the Commons vote for a replacement of the SSBN's (the UK's only active nuclear weapons launch platform) is a bitter development for him. Corbyn's removal as Labour Leader is probably imminent.
Successor Class Basing and Cost Problems Remain
Problems of uncertain basing (ejection from Faslane submarine base in Scotland) and guaranteed rapidly escalating costs of the Trident replacement fleet remain. This is evinced by all but one of the MPs from Scotland voting against replacement.
A side note is that UK commentators seem to harbour a sexist surprise that the new female Prime Minister, Theresa May, says she would be willing to press the nuclear button without hesitation in a nuclear exchange. The effectiveness of a nuclear deterrent relies on assurance to an enemy that they would be destroyed in a SSBN/SLBM first or second strike situation.
Successor is probably a temporary name with a name more historical and British likely to replace it in years to come. The up front build cost of the 4 Successor class is currently estimated at UK £31 Billions total. This represents an injection of money into needy UK regional areas - a financial argument on top of national defence arguments for the Successors.
Russia Unhappy at Trident Vote but Happy With Turkey
Russia, under Putin, would not be happy. Russia would have preferred that its long moral/propaganda (and perhaps financial) campaign that the UK undergo a process of unilateral nuclear disarmament has been frustrated once again. A disarmed UK would weaken NATO - a weakened NATO may be less threatening. A weaker NATO would permit lower Russian defence spending.
Nevertheless, this week has not been all bad news for Russia. With the near coup in Turkey, the important Turkish component of NATO is in temporary factional disarray. The Russians and US would be busy researching Turkey's latest troubles, separately.
See the Submarine Matters articles on UK-Trident Replacement and Brexit.