At the centre of debates about green belts is the question of trust. In theory it should be possible to build on a very small proportion of the nation’s green belts in such a way that affordable housing and sustainable communities are created, and more people have more and better access to nature than before. In practice few people trust that this will happen, as the available evidence is that we will get instead a smearing of developers’ standard products across the countryside, for sale at inflated prices.

The promise of what’s called the North West Cambridge Development is that it will indeed achieve these good things. Here the University of Cambridge is turning 150 hectares of what was flat, inaccessible and somewhat featureless farmland, located between the city and the M11, into a billion-pound urban district the area of which is not much smaller than the historic centre of Cambridge itself. Three thousand homes are planned, half of them affordable, plus 2,000 postgraduate student bed spaces, 100,000 sq m of research facilities, and the schools, shops, surgeries and the like needed to sustain them. Two new public parks are being created, one between the new development and the old city, the other a series of lakes and mounds that buffer the sights and sounds of the motorway.

The development is motivated by the extreme effects of growth in Cambridge, resulting in house values that have priced out key workers, including researchers and young academics, without which neither university nor city can function. In this way Cambridge acutely experiences pressures felt in other parts of the country, which has put it at the forefront of finding ways to do something about them. Change doesn’t happen quickly: discussions of expansion have been going on since the 1980s, with the current plans in development for over a decade.

There is a patent desire to be responsible and exemplary in everything. The North West Cambridge Development sets out to achieve high levels of sustainability, including many photovoltaic cells to gather solar energy, low levels of car use and the recycling of rainwater for irrigation and the flushing of toilets. It has been masterminded by the multinational AECOM, which is one of the largest engineering and design consultancies in the world, with landscapes by Townshend, who have worked on large commercial developments such as King’s Cross in London. An array of well-respected architects have been brought in to design individual buildings: the Stirling prize winners Alison Brooks, Witherford Watson Mann, Wilkinson Eyre and Stanton Williams; Marks Barfield of London Eye fame, the Dutch practice Mecanoo and Muma, best known for their makeover of the Whitworth Art Gallery in Manchester. I am told that they also wanted “young” architects, although these practices are almost entirely led by over-50s.

The University of Cambridge primary school at Eddington. Photograph: Morley von Sternberg/North West Cambridge Development

The plan is now taking physical form and, so far, it is doing what it said it would. The first homes have been completed in Eddington, which is the name given to the first phase. Residents have started moving in. A “market square” is complete. A new Sainsbury’s opened last week. A primary school has been open for two years. Swirles Court, housing for the graduate students of Girton College, is also complete. Unusually, in comparison with most commercial developments, it is the affordable housing and the shared facilities, rather then the more profitable high-value homes, that are being built first.

Cambridge has never been a throbbing metropolis and its suburbs less so. By the time you get to the environs of north-west Cambridge the city is petering out into detached and semi-detached houses. Yet Eddington is in the form of apartment blocks, three to five storeys high, in density more like an inner suburb of a large Victorian city, with the intention of building a lot of homes without using up too much space. It’s a surprising typology, but it makes sense.

The architectural style is bricky, rectangular, austere with a few outbreaks of playfulness. Ludwig Wittgenstein, who spent his last months in nearby Storey’s Way, once praised the plain Georgian terraces of Dublin for having “the good taste to know that they had nothing very important to say”, and the same might be said of this style. Metropolitan types call it the “new London vernacular”, but it turns out it’s at home here too, on the edge of the fens. Its best qualities are its thoughtfulness – the unusually high ceilings in ground-floor flats, the proportions of windows, the use of galleries with expansive views to give access to upper-level flats.

The more public buildings loosen up a bit, though not too much. The school, by Marks Barfield, is an elegant flat doughnut with a calm, protected space in the centre. Muma’s nearly complete nursery school and community centre, designed for things like “dance classes or zumba, Brownies or film clubs, fashion shows, weddings or fairs”, will offer a lively inner world of contrasting volumes, while still being quite quiet on the outside. So the overall effect is of a development that is thoughtful and considered but also, even after making due allowance for its unfinished state and the fact that plants need to grow, overdoing its sobriety.

Eddington’s cricket pitch and adventure playground. Photograph: North West Cambridge Development

Here the landscaping, which should be crucial, is unfortunately the weakest part. It should soften and animate and make places distinctive and sociable. What’s there, all good quality to be sure, has its moments – there’s a nice grassy swale running through the development that’s part of the rainwater system – but it tends towards the generic. The market square (where, for now, no actual markets are planned) is a could-be-anywhere bit of tasteful corporate design, for which some funky benches are not a sufficient antidote. There’s a long straight pedestrian-friendly street that looks promising as a place to congregate, but its hard and rectangular planters are oddly discouraging. The beige Mondrians of paving too often beat the planting. You can’t yet see spaces in which it would be a positive delight for children to play.

More fundamentally the distribution of design intelligence is out of whack. In a way that almost always happens in projects of this scale the big efficient companies like AECOM are asked to make the really big decisions, whereas the Stirling prize winners and “young” architects get to play with a fairly limited range of choices about proportion and disposition. If the imagination and skills of the latter had been applied to the orchestration of a potentially rich array of shared spaces, and to an overall idea of the kind of place that is being created, it would have turned North West Cambridge from a good to a world-beating piece of planning.

But these weaknesses should not detract from what is likely to be a fundamental success of the development. To the basic question to be asked when building on green belt or any green land – is it better than it would have been had it stayed as fields? – the answer is yes. More people will enjoy richer forms of nature in the new parks than in the past, and many will find homes at high levels of design and sustainability. The clout, wealth and wisdom of the university has been vital in achieving this, but if the model can be followed in other green locations across the country we might find a way to create large numbers of decent homes and respect nature at the same time.