There is something quite unique about Queen Elizabeth stepping on board the ship, HMS Queen Elizabeth.
It’s not just because it’s the aircraft carrier that bears her name, it’s also because she is the person to whom each and every sailor on board that vessel has sworn an oath of allegiance to.
And, for them, it was no doubt an honour to have the 91-year-old Monarch on board the biggest ship ever built for the Royal Navy.
But there is much more to this Royal Navy vessel than size; 65,000 tonnes makes for a big ship; the 700 staff needed to get her afloat makes for a big Ship’s Company.
There are questions about the multi-billion cost of the Queen Elizabeth and her under-construction sister-ship, the Prince of Wales.
Are these aircraft carriers the right sort of investment in national security when the threat the UK faces comes from lone terrorists or from ISIS/Daesh in Syria?
Some would put forward the case that the £3.1 billion cost could have been better spent on intelligence for the cash-strapped MI5 or MI6.
That money could have helped to prevent a Manchester attack or a murderous rampage on London Bridge.
But the argument you hear from senior defence officials in Portsmouth, is that the future is an uncertain space and so the UK needs this big hulk of grey metal to act as an insurance policy against all manner of unforeseen threats.
Some of those threats we can predict: Russia, North Korea, a rogue state or an insurgent group which can be attacked from the mobile platform that this aircraft carrier will provide.
Some of those threats are yet to rear their heads and are yet to be identified.
Both the Defence Secretary and the First Sea Lord told me on Thursday that HMS Queen Elizabeth – and HMS Prince of Wales - will provide the UK with an adaptable, flexible defence resource for many decades to come.
But an aircraft carrier needs both aircraft and a working escort of naval destroyers. Right now, it has neither.
No one can guarantee the full order of F-35 fighter jets. The UK had initially intended to buy more than 130 of the new generation planes – many of which will fly from this carrier. It might now order only half that amount.
And the Royal Navy destroyers, which are required to sail with and protect any aircraft carrier, are currently beset with mechanical problems.
Admiral Sir Philip Jones, the most senior naval officer, admitted that the engines on the new Type 45 Destroyers “have given us some challenges in the past few years”.
It proves that investment decisions in one area of UK defence can be severely offset by poor decisions elsewhere.