The BBC and ITV’s newly announced BritBox – a joint streaming service – is a bizarre example of British broadcasters deciding “to work together in the national interest”, to borrow a phrase currently popular in Westminster.

Facing potentially ruinous competition from US streaming giants, led by Netflix and Amazon Prime, Britain’s oldest broadcasters are trying to claim a Blighty stake in the increasingly global, but largely American-financed, TV market. The venture submerges (if not necessarily suspending) decades of rivalry between the BBC and ITV so intense that both sides keep their schedules secret until the last minute to avoid giving the other any advantage.

Like an abandoned prototype from a decade ago, Project Kangaroo, BritBox will be subject to regulatory approval. Last time, to the delight of Rupert Murdoch, who then owned Sky, the Competition Commission ruled that a BBC-ITV collaboration would result in an unfair concentration of power.

But the TV landscape has changed so much that the older British broadcasters are almost powerless against the global box-setters. If the Competition and Markets Authority (which now scrutinises deals) and the media regulator Ofcom were to block BritBox, it would lead to incredulity and likely calls for judicial review. With Sky now owned by Comcast, it helps that Murdoch newspapers are unlikely to be much of a dog in the fight this time.

However, due to another TV trend – the rise of independent production companies – BritBox faces issues at least as problematic as the external pressures that barbecued Kangaroo.

A streaming service lives or dies by the content rights it owns, or can buy. But of the top 25 programmes in this newspaper’s best TV shows of 2018, only one, Doctor Who, was wholly owned by the BBC. Three huge BBC hits – Bodyguard, Killing Eve and Poldark – were made by independent producers World and Mammoth, and Sid Gentle.

Doctor Who – one of the few smash-hits the BBC actually owns. Photograph: BBC

To complicate matters, World and Mammoth are now part of ITV, which has recently followed a canny strategy of gathering more than 60 independent production companies under the umbrella of ITV Studios. This has led to the oddity of ‘BBC shows’ having their streaming rights sold by ITV to Netflix, as happened with Bodyguard and Poldark.

One of the key imponderables of BritBox is whether ITV Studios will be able to persuade its partners such as Mammoth to license material to BritBox rather than the streaming behemoths. The new service will need to be exceptionally well-funded to match the huge rewards Netflix and Amazon can offer.

With the BBC now owning so few of its hits – the reason it could not avoid losing the Great British Bake-Off to Channel 4 – what the Corporation is mainly putting into BritBox is its vast archive, from the days when it did own sole rights to most shows.

There were hints of a possible structural tension in the venture when ITV chief executive, Carolyn McCall, stressed on the Today programme that “ITV will create original content” for the service. What went unsaid was that it would be hard for the BBC to do so, without undermining the case for the licence fee and the iPlayer, two of its pivotal assets. The fact that McCall was only able to announce she was in the “final stages” of an agreement with the BBC, rather than formally launching the scheme, may also suggest how legally and logistically complex the idea is. (The absence at this stage of Channel 4, a previously rumoured partner, is another sign of the agonising calculations networks are having to make.)

As it would be politically disastrous for the BBC to be thought to spend significant licence fee cash on BritBox, a crucial decision will be the price charged for the service. Making the announcement, McCall refused to be drawn on industry guesses of around £5 per month. (A Netflix subscription in the UK costs from £7.99 to £9.99; an Amazon Prime Video membership is £5.99 monthly, with various student or new-user discounts.)

Whatever it costs, BritBox may also hold a clue to the far future of British broadcasting. The traditional ways the BBC and ITV are funded – by licence fee and advertising income – are both under considerable pressure. This has forced broadcasters to examine the possibility of ultimately moving to subscription models, which the rise of the streamers has made to seem the natural way of getting TV, especially for younger viewers.

So might future TV fans in Britain be offered a choice between, or combination of, subscriptions to something like Sky, Netflix, Amazon and BritBox?

It is a huge question whether the ITV model of multiple production companies could ever be married long-term with the BBC structure of 22,000 employees and eye-watering pension commitments.

But the hugely risky BritBox project demonstrates the extent to which traditional British ways of making and paying for TV must now be subjected to thinking outside the box.