A quiet nature reserve could soon become a thoroughfare for heavy delivery lorries – prompting furious conservationists to launch a campaign to protect the leafy trail.

Heavy-goods vehicles (HGVs) weighing 26 tonnes would drive along a stretch of the Parkland Walk in Highgate under plans to convert an old railway cottage into a seven-bedroom home with basement.

More than 500 people have signed a petition against the proposal, which protesters say poses a danger to users of the old railway line – particularly children and the elderly.

Cathy Meeus, treasurer of the Friends of Parkland Walk, said: “It’s an outrageous abuse of this nature reserve.” She added: “A lot of families use it to go to and from school. Elderly people could suddenly find their right of way blocked by construction traffic.”

A historic agreement bans vehicles from accessing the cottage, which is on a former section of the woodland walkway.

It is surrounded on nearly all sides by the Parkland Walk and does not back onto a street.

But that covenant could now be broken to allow investment banker Sebastian Eiseler to extend the house in Francis Place, off Holmesdale Road, and dig a basement guest room and playroom underneath.

Ms Meeus claims that the current owner was able to buy the cottage at a knock-down price because Haringey Council forbids vehicles from accessing the property.

Mr Eiseler won planning permission earlier this year for the conversion plans. But he has now lodged a construction management plan with Haringey Council, which revealed that lorries would drive along the Parkland Walk over four months.

The proposal has infuriated residents and community groups – including the Highgate Society.

Many are concerned about the impact on trees, plants and wildlife – including protected bats which live in disused railway tunnels next to the cottage.

Sara Smith, of Cascade Avenue, Muswell Hill, said in a statement: “The application benefits only a private individual.

“Please don’t let the power of the wealthy of London override the rights of those less fortunate.”

The Friends of Parkland Walk, a group dedicated to protecting the trail, is furious that it was not consulted on the plan. It only learnt of the application when it was submitted last month.

The Parkland Walk was declared a nature reserve in 1990, and its management plan states that driving on the trail is “kept to a minimum”.

Mr Eiseler did not respond to a request for comment before the Ham&High went to press.

Sign the petition here.