The result was the Resolution class of nuclear submarines - Resolution, Repulse, Renown and Revenge - each armed with up to 16 Polaris nuclear missiles.
Their design, construction and delivery is one of the triumphs of British industry and defence in the 20th Century. Four submarines, each as complex as the rockets aiming for the moon at the time, with a weapon system never before operated by the Royal Navy, and two new naval bases - one at Faslane for the submarines, one at nearby Coulport for the missiles - delivered inside seven years... and on budget.
While shipwrights and engineers toiled on building the submarines themselves at Cammell Laird on Merseyside and Vickers at Barrow, a small town with supporting facilities sprang up on the right bank of Gareloch which would become HMS Neptune.
Just weeks after the Royal Navy's new base on the Clyde opened in the spring of 1968, HMS Resolution conducted the first deterrent patrol (round-the-clock patrols did not begin until 1969 as the remaining R-boats entered service).
Submerging for up to three months at a time, the crew were almost entirely cut off from the outside world for the duration of the patrol.
No personal communications off a boat was permitted - an order which persists to this day. They received a regular update from their loved ones, known as a 'familygram', restricted to just 40 words.
If the messages contained bad news (such as the death of a family member or a request for a divorce), it was withheld from the intended recipient: the mission was more important than the man.
These hardships aside, life in an R-class submarine was considerable cleaner and more spacious than the old diesel-powered boats. Living in apparent luxury, deterrent boat submariners were dubbed 'bomber queens' by their contemporaries or 'Polaroids' after the popular make of instant cameras.
The only limit to a deterrent patrol - apart from the endurance of the men on board - was the amount of food which could be stored aboard. The longest patrol - 108 days - was completed in 1991 by HMS Resolution.
By the time of that mammoth patrol, the R-class and their missile system were nearing the end of their active lives and a new generation of deterrent boats was taking shape in a huge ship hall in Barrow.
When the final R-boat patrol ended in 1996, the class had completed 229 missions, 69 by HMS Resolution alone.
- For more information about the Polaris era, visit the Silent and Secret exhibition at the Royal Navy Submarine Museum in Gosport: