Life on board a Trident nuclear submarine
As you would imagine, it's not easy getting on board one of Britain's nuclear submarines.
And nor should it be. After all, these are pretty much the most powerfully destructive weapons on earth.
I first approached the Ministry of Defence about making a programme on the future of Trident in the summer of 2009.
Some 15 months, numerous meetings, e-mails and phone conversations later, I finally clambered on board HMS Victorious, one of Britain's four "bomber" submarines, berthed at Faslane.
And it's not easy to get on board for another reason; three large men, a reporter, and a pile of filming equipment takes a bit of squeezing down a small hatch and some 30ft (9m) of ladder on to the main deck of these most secret of vessels.
But the wait, and the squeeze, was well worth it.
Not least because the change of UK government, and its subsequent decision to tackle the deficit quickly, has made Trident more of a story than ever.
With 8% cuts in the defence budget, there has been a lot of pressure on ministers to think again on Trident.
The argument against renewal goes something like this: it was designed for the Cold War, we're not in imminent danger from another nuclear weapon state, and it costs a lot of money; so why are we spending all this money on something we hope never to use?
For the Defence Secretary Dr Liam Fox it's very simple: regimes like North Korea are trying to develop nuclear weapons, and we cannot gamble with Britain's future security.
For Trident's many opponents, it's also very simple. They regard it as immoral, illegal, and think we should be spending the money on other things.
This is a huge issue, and in the end, it comes down to what we would do to defend our country, what kind of country we would like to be.
The long wait to make this programme was worth it for another reason.
We are able to show just a glimpse of the strange lives the (all-male) crews of the bomber submarines lead.
On purely logistical grounds, these 500ft-long (152m) vessels are fascinating pieces of machinery.
They can carry up to 16 missiles, each armed with multiple warheads many times more powerful than the bombs dropped on Japan in 1945.
When they leave the Clyde and head out on patrol, they submerge for a whole three months.
In that time, they will not contact base.
The captain alone decides where they go and when. Their job is to hide, become a "black hole" in the water, ready to fire weapons of unimaginable power.
The 160 crew members depend upon one another every minute of the day.
Their bunks are tiny, living quarters cramped. They can only tell the time of day from whether they are eating breakfast, lunch or dinner.
It's a world of discipline, and absolute certainty of purpose, operating in a world which is much less certain.
BBC Scotland Investigates: Who Needs Trident? will be shown on BBC One Scotland at 2245 GMT on Wednesday.