Philip Pullman is used to epic battles - he has created enough of them, particularly in the bestselling trilogy His Dark Materials, the first book of which was recently turned into the Hollywood blockbuster The Golden Compass. The author’s latest engagement, however, involves not the sinister foes of his own vivid imagination, but a rather more prosaic, real-life breed: garden grabbers.

In what’s been dubbed the Battle of Cumnor Hill, Pullman has spoken out in support of a group of 60 residents of this green, leafy area, in outer west Oxford, who are trying to stop their neighbours selling their houses and gardens for redevelopment.

Pullman lives on the outskirts of the city and his attachment to it is well known, as it has inspired some of his most famous work. Last year, he intervened to protect a historic boatyard in the north of Oxford from being developed into flats.

Now he fears that Cumnor Hill will succumb to the same kind of “uglification and destruction” that threatens much of the university city if plans for various high-density schemes are approved by local planners. “I am completely against this,” he says. “I want as few of these new developments as possible . . . They seem to be spreading everywhere. I wish they would stop.”

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Many of those who live on the hill – including Canon John Rees, legal adviser to the Archbishop of Canterbury, and Professor Chris Perrins, Warden of the Swans – bought their detached homes in order to enjoy the peaceful, semi-rural lifestyle the area offers. On the hill, where the Victorian poet Matthew Arnold once strolled, wildlife abounds and the views are stunning. All that is now under threat.

“We risk losing our family homes and large gardens to developers and our trees to a vista of brickwork,” Rees says. “We get letters from developers who go out in helicopters, spot green areas that look like open land, then mailshot the people who live there.”

For the past three years, a chasm has been widening between those determined to preserve Cumnor Hill as it is, and homeowners and developers who want to reap the financial benefits of subdividing and building flats on such large plots. It is a classic example of “garden grabbing”, a practice so widespread in the southeast of England that Greg Clark, Conservative MP for Tunbridge Wells, has tried – so far without success – to have it outlawed via a private members’ bill.

Only a handful of developments has been approved by planners at Vale of White Horse council, who have rejected others. Mike Gilbert, development control manager for the council, says that roughly half a dozen separate applications are now under consideration.

Gilbert says that, while both the Vale and Oxford need more housing, his team must consider the impact on those already living on the hill, as well as on wildlife and the environment. “We have to make sure that any changes do not make the hill a brick vista.”

A precedent could be set next month, when the result is due of an appeal against the planners’ rejection of a scheme to build a block of five flats, six houses, a coach house and a car park on the site of a single home. “It is the first appeal and will set some principles,” Gilbert says.

It is all too much for Malcolm Taylor, a recently retired sales director, who lives with his wife, Diane, at 31 Cumnor Hill. “There are now four separate applications for development within 40 yards of my house, including the one under appeal,” he says. “Next door, there is an application to take down the existing house and build two large detached houses, a block of five flats and two semidetached houses on the site – a total of nine dwellings.

“We may come across as incredibly nimby,” Taylor adds. “I appreciate that. But this is one of Oxford’s last great green hills. The problem is that there is a lot of money involved, and for some people that is tempting.

“We estimated that the property next door would sell in its current state for about £800,000 – but in its developed state, with nine dwellings, it could be worth £4.5m.”

The fear about the rash of applications is that, eventually, all of Cumnor Hill will be turned over to high-density living. I must declare an interest. My parents live on Cumnor Hill, and their grandchildren have spent summers running wild in their magical sloping garden, marvelling at deer, foxes, bats – even a shy badger. The tranquil views from the terrace are of mature trees and distant hills. Recently, anxiety about the growing number of development applications has driven my parents and many of their neighbours to despair. But they are not giving up without a fight.

“Many residents signed a petition to turn part of the hill into a conservation area to protect the trees,” Rees says. “They did not buy on the hill to make a killing, but because this is where they want to live.”

The battle of Cumnor Hill is not over yet.

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