What a glorious photo opportunity: the new pride and joy of British sea power, HMS Queen Elizabeth, largest warship ever built for the Royal Navy, this week sailed from the Firth of Forth for sea trials.

Here is a 21st-century ‘castle of steel’ to strike terror into the nation’s enemies.

Except the ship is nothing of the sort. HMS QE and its half-built sister, Prince of Wales, are giant embarrassments. They are symbols of almost everything that is wrong with British defence policy.

Their principal promoter 15 years ago was the First Sea Lord, now Admiral Lord West of Spithead, who went on to become a Labour security minister, and more recently an enthusiastic writer of letters to newspapers, explaining why ‘his’ carriers are wonderful.

He urged that, if Britain was to be a modern sea power, a worthy ally of the U.S., we needed giant platforms to carry the American F-35 fighter then under development.

HMS Queen Elizabeth and its half-built sister, Prince of Wales, are giant embarrassments. They are symbols of almost everything that is wrong with British defence policy

Some of us said from the outset that the new carriers reflected delusions of grandeur, and that the F-35s looked like becoming much too pricey for Britain’s status as a medium-sized nation.

How much smarter it would have been to build a couple of cheap ’n’ cheerful naval platforms from which to launch drones and low-tech aircraft. For that, one could almost have welded steel plates on top of tanker hulls, to create acceptable flight decks.

Anyone could have seen that defence was destined to remain under huge pressure. And it should have been taken into account that the cost of the ships and their planes would soar, as it always does.

What the Navy urgently needed was a large flotilla of small, simple ships to guard our shoreline and look after our interests overseas in regard to piracy, illegal immigration, terrorism and so on.

But no, the admirals — West and his successors — were insistent: only the behemoths would do. There were still enough sensible people in the Ministry of Defence to prevent this lunacy coming to pass, but for one misfortune: in 2007, Gordon Brown became Labour prime minister. In case you failed to notice, he was, and remains, a Scot.

I doubt Brown would have spent sixpence on the aircraft carriers, except for one fact: he cared passionately about Scottish shipyards, and creating jobs in marginal constituencies. When contracts were signed for the new ships, Rosyth on the Firth of Forth became their birthplace.

For the past decade, convoys of dumper trucks filled with Scottish currency, almost all provided by English taxpayers, have headed north to fund the carriers’ construction. The original budget was £4 billion, and the monsters were scheduled to enter service in 2015.

Today, costs are already over £6 billion and counting, while until at least 2020 Queen Elizabeth will do little beyond hosting ballroom dancing classes for her crew, as extensive sea trials are carried out.

Because of ballooning costs, her sister carrier, Prince of Wales, would almost certainly have been cancelled, but the canny Scots ensured that penalty clauses meant it would cost less to complete than abandon the ship.

Today, costs are already over £6 billion and counting, while until at least 2020 Queen Elizabeth will do little beyond hosting ballroom dancing classes for her crew, as extensive sea trials are carried out

Yet, as critics pointed out from the start, the ships were the least of the story: Lockheed’s F-35 fighter jet programme has gone disastrously awry, terrifying the Americans with its £150 billion cost overrun and seven-year delay, so that it has been dubbed ‘the jet that ate the Pentagon’.

At the outset, Britain planned to put 36 F-35s on each carrier. So stupendous is their cost that this has shrunk to 12. An unhappy naval officer muttered a year or two back: ‘Just so long as we can have enough to cover the flight deck in photos.’ The empty hangar space will be filled with helicopters, commandos, snooker tables — no, I am teasing about the last bit.

Sailors say that Queen Elizabeth will be useful for disaster relief missions. But a Channel ferry could do that job better as it can operate inshore, as the 65,000-ton giant cannot.

Worse, big ‘flat-top’ aircraft carriers will be vulnerable to the new generation of anti-ship missiles, which the Chinese and Russians are manufacturing in quantity, and which even such a nation as Iran is likely to acquire.

When either of our carriers puts to sea, almost the entire surface warship strength of the Navy will need to be deployed to protect them.

I have compared these boats to the ancient Egyptian pyramids: they have consumed immense resources while possessing almost zero utility. At least the pyramids are amazing to look at; I doubt in years to come a single tourist will visit Portsmouth to see the QE rotting at its moorings.

If I sound intemperate, it is because many people who care passionately about Britain’s defences have been warning for years that the carriers would prove a disaster.

There is a multi-billion-pound hole in the defence budget, and especially in Navy funding, which seems likely to be filled by yet again slashing the Army, a deplorable and short-sighted expedient.

Because of the fall in the pound, the F-35s are even more unaffordable, and thus their delivery may be slowed yet again. Until some planes arrive, the QE will presumably ferry the Royal Family overseas — they may get a Britannia replacement after all!

A bold government would adopt a drastic but sensible option: mothball both carriers and cancel the F-35 jets, whatever the penalty costs, and buy modest ships which the Navy can make real use of.

When the Queen christened the new carrier, her speechwriter caused her to describe this as representing ‘a new phase in our naval history’. Indeed it does, and not a good one

The Navy’s website today lists the types of warships it owns — frigates, minehunters, destroyers and so on — but wisely does not give their respective numbers, because these are so embarrassing: it has just 19 significant surface vessels, together with some submarines and small craft.

Most sailors are privately as miserable about the burden the carriers impose on them as are soldiers and airmen. Yet the political cost of adopting the most rational course — sailing the QE into the North Sea and opening its seacocks to let the water flood in — is deemed unacceptable.

All nations are prone to equip themselves to fight the previous war, rather than the next. But Britain is in an especially bad fix, bereft of a credible strategic vision, because nobody dares even to think about the cost of preparing — for instance — to participate with NATO in a showdown to defend the Baltic republics against Russian aggression.

Our cyber-defences are negligible, yet these seem far more urgent and relevant than the Trident nuclear replacement. There is a fair chance we shall get through another generation without a nuclear showdown, God and President Trump willing.

There is no chance at all, however, that we shall avoid serious cyber-conflict, which could do undreamed of harm to infrastructure and the very heartbeat of the nation: consider the ranging shot that North Korea recently fired at computer systems around the world, including those of the NHS.

Our defences and security are in poor shape, partly because almost all eyes, including those of ministers, are focused on the domestic terrorist threat, rather than on foreign state enemies.

When the Queen christened the new carrier, her speechwriter caused her to describe this as representing ‘a new phase in our naval history’.

Indeed it does, and not a good one. It is a symbol of our weakness; of the irrelevance of much of our defence policy to the perils our children and grandchildren are likely to face from Britain’s enemies.