Plans for an assault course, waterfall and running track dubbed a “millionaire’s playground” have been rejected.

Buckinghamshire Council refused to grant applicant Mrs Sara Aga a certificate of lawfulness for her plans to transform a huge agricultural field.

She proposed to create a “landscaped private recreation area” to the rear of a huge house on Witheridge Lane in Penn in between High Wycombe and Beaconsfield.

Plans included planting a wildflower meadow for bees and moths, as well as installing a wild swimming pond, surrounded by 600 metres of new hedgerows.

The pond would have included a boardwalk, jetty and diving platform, a deck with a hut and even a waterfall, complete with “layered rocks”.

A master plan submitted to the council also shows beehives, orchards, a machinery storage building and a mesh steel security fence around the perimeter of the site.

Pictures also show a 100-metre uphill sprint track and several design ideas for “trim track stations” –elements of an assault course – including monkey bars, a tyre run, a wobbly bridge, push up bars and other equipment.

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At the time of the decision on the application, the plans had drawn 21 letters of objection from local people.

One read: “Everything about this application is appalling: an attempt to arrogate ancient farming land, which is enjoyed by hundreds of local walkers, and develop it into a ‘millionaire’s playground’.”

Others claimed the applicant wanted to turn “harmonious fields into a grotesque eyesore playfield and an out of place fortress”.

Some took issue with the impact the plans would have on the “irreplaceable habitats” in ancient woodland to the east and south of the site, in which has “immeasurable damage has been inflicted on the local flora and fauna”, including “deer, red kites, bats, rabbits, owls, butterflies and bees”.

A council officer noted that the application was only asking for permission for a proposed use of the land, despite the building work that would be involved.

They said this meant that a certificate of lawfulness for should not be granted for the proposals because they “constituted a material change of use of the land, for which planning permission is required”.