Right up to the moment the polling stations closed at 10 p.m. last Thursday in the U.K., the political pundits were unwavering in their forecasts: neither Prime Minister David Cameron’s Conservatives nor the opposition Labour Party wielded enough firepower for an outright win in Britain’s 2015 parliamentary elections.

Had Labour emerged with the most seats in the House of Commons, its hopes of forming a viable government would have required the support of the fiercely anti-nuclear Scottish National Party. This was a worrisome prospect for advocates of strategic nuclear deterrence, who feared that a weak Labour leadership would inevitably cave in to SNP demands and scrap plans to renew the U.K.’s submarine-based Trident ballistic missile force.

If on the other hand the Conservatives had remained the largest party in a hung parliament, the expectation was that they would seek to re-establish their coalition government with the Liberal Democrats, a party which has campaigned to replace the continuous at-sea deterrent (CASD) — requiring four nuclear ballistic missile submarines (SSBN) — with a part-time version employing nuclear-armed cruise missiles.

By the early hours of Friday morning, however, it was clear that an unexpected surge in the right-of-center vote had given Cameron a slender overall majority in the Commons and the keys to 10 Downing Street for five more years.

With the prime minister vowing to retain the Trident CASD and procure new strategic missile submarines to replace the existing Vanguard-class boats, it was the best possible result both for the Royal Navy and for shipbuilder BAE Systems, reactor plant provider Rolls-Royce, through-life support contractor Babcock and the 850-or-so other companies who are, or will be, involved in the renewal program.

In 2011 the then Conservative/Lib Dem coalition decided to invest $4.67 billion in a five-year assessment phase for the Successor SSBN program (the figure has since grown to $5.14 billion). Activities in 2015 include $389 million for advanced design work by BAE Systems and the finalizing of plans for new manufacturing facilities at its Barrow yard.

The so-called “main gate” investment decision is expected in early 2016, when the new government will announce its intention to replace the four Vanguards on a one-for-one basis or whether it believes CASD can be guaranteed with just three new boats.

Meanwhile the lifespan of the current SSBNs – which were commissioned into the Royal Navy between 1993 and 1999 – is being extended by nine years, allowing the in-service date for the first of the Successor submarines to be pushed back to 2028.

Aligning the procurement timescales for Successor and the U.S. Navy’s Ohio-class replacement has allowed the U.K. to exploit transatlantic collaboration in several areas, notably the design of the Common Missile Compartment (CMC) and the nuclear steam-raising plant, and the integration of sonar arrays and combat systems.

Britain is also participating in the U.S.-led life-extension program for the Trident II D5 missile, which is expected to prolong the Lockheed Martin-built air vehicle’s service career through to the 2040s.

The warheads – which are designed, built and maintained by the Atomic Weapons Establishment at Aldermaston, 50 miles west of central London – are expected to last well into the late 2030s and possibly beyond, so a decision on a replacement warhead has been deferred until 2019.

However, as a result of its Strategic Defence and Security Review in 2010, the coalition administration decided to shrink Britain’s stockpile of nuclear warheads from 225 to 180 by the mid 2020s – a 65 percent reduction since the end of the Cold War – and cut the the number of operationally availble warheads from 160 to 120. The latter target was achieved by January this year.

In similar vein, the number of operational missile launch tubes in each Vanguard submarine has been cut from 12 to eight and the maximum number of warheads carried on a patrol from 48 to 40. Successor will also have eight tubes instead of the dozen originally planned.

According to the Ministry of Defence, the renewal program is expected to cost between $27.27 billion and $36.46 billion (at 2013/14 prices), including $20.1 billion to $25.5 billion for the submarines. In service, the Successor/Trident deterrent will account for 5 to 6 percent of Britain’s annual defense budget.

It’s a high-stakes game. Having withdrawn its air-dropped nuclear bombs from service in 1998, Britain is unique among the major nuclear weapons states in relying upon a single delivery platform. And with Russia again testing NATO’s readiness on several fronts, North Korea threatening nuclear missile strikes on the U.S., and Iran apparently trying to acquire a similar capability, now is probably not the time to consider further reductions in deterrent capability.