Three months after Princess Margaret's death, the Sussex home of her former husband Lord Snowdon is up for sale.

And whoever shells out the £1.5 million asking price will become the owner of a unique property, described by 72-year-old Lord Snowdon as his "magical secret domain".

He spent much of his youth at Old House, located in the grounds of the Nymans estate, 11 miles from Gatwick Airport.

Every year thousands of people visit Nymans, now owned by the National Trust, to see its perfectly sculptured gardens and the house built by Lord Snowdon's grandparents which was destroyed by fire in 1947.

Yet few get the chance to discover the secrets of Old House, in the grounds nearby.

Clive Aslet, editor of Country Life, accompanied his friend Lord Snowdon on one of his last visits to the property.

Describing the visit, he says: "Old House has a slightly miniaturist quality, like a child's story-book illustration.

"It is the spiritual child of Nymans, his grandparents' theatrical, romantic house, and its contents recall the fun that a creative family has had in making, sometimes faking, this place."

The house is, he says, so private, even aircraft noise is miraculously banished.

Old House started life as three cottages and was developed by Snowdon's grandmother as a destination for afternoon walks.

She left it to her son Oliver Messel, a stage designer and artist, but he had no use for the house and in 1958 gave it to Lord Snowdon, then Anthony Armstrong-Jones. He married into the Royal Family two years later.

Lord Snowdon recalled of his grandmother, Mrs Messel: "She would walk to it through the woods for tea, which had been miraculously laid out before she arrived.

"It was my grandmother being Marie Antoinette."

Over the years, Old House underwent numerous alterations but always retained the cosiness favoured by Mrs Messel.

At one stage it had its own staff of eight gardeners, despite having no garden of its own.

The house, on the market with FDF Savils, is full of fascinating objects, each with a story to tell.

The HP sauce-stained shelves are racked with plates painted by family members and fired in the pottery installed at the property by Lord Snowdon.

The wash basin in the downstairs lavatory is another of Lord Snowdon's pottery products. He asked his dentist to drill a hole for the outflow pipe.

Also in the kitchen is an old oak table on which names such as (Viscount) Linley and Ken Tynan, the late theatre critic, have been carved with a chisel.

The house also contains a darkroom set up by Lord Snowdon, a leading photographer.

The Jacobean four-poster bed, glass display cabinet of lead soldiers and other furnishings are not included in the sale.

But prospective buyers can hope its vendor will leave behind the seat mounted on a pulley which whisks visitors from the house to the lake and is nicknamed The Chute.

Old House is being sold leasehold by the National Trust.