Newhailes in East Lothian is a Sleeping Beauty of a garden. Take your imagination for a walk and you may well encounter Dr Johnson discoursing with Lord Hailes in the derelict tea-house, or get a whiff of Archie Weir arguing with his unforgiving hanging judge of a father, the Lord Justice-Clerk, in Robert Louis Stevenson’s Weir of Hermiston.

This early example of an improved estate, outside Musselburgh, east of Edinburgh, is one of the least changed designed landscapes in Scotland, and its estate records are remarkably intact. The original house and its owners were early beacons of the Scottish Enlightenment, the period of intense intellectual and cultural achievement centred on nearby Edinburgh. It was called Whitehill, and was built by the architect James Smith for his own use in 1686.

Smith had studied in Italy, and was an admirer of Palladian themes, as we see in Drumlanrig Castle, one of his most famous buildings. The exterior of Whitehill was, by contrast, built in a plain, symmetrical style. The main embellishments were kept for the interior - shell cornice mouldings, Ionic columns, magnificent chimney pieces.

In 1707 (the year of the Act of Union), the house passed into the ownership of the Dalrymple family, many of whom were prominent as politicians, jurists, judges and advocates at the Scottish Bar. The first Dalrymple owner renamed the property Newhailes and planned to use it as his Edinburgh town house. Dr Johnson, who visited the house with Boswell during their tour of the Hebrides in 1773, described the magnificent library as “the most learned room in Europe”.

The Dalrymple family lived there until 1997, when it was given to the National Trust for Scotland. Generous lottery funding has been secured, and a major programme of restoration is about to begin.

One of the first things to be decided, says Robert Grant, gardens adviser to the NTS, is what version of the gardens should be restored, bearing in mind that map references over a 250-year time-span indicate differences as well as similarities. The Victorian garden may be better documented, but was the Enlightenment garden 100 years earlier more significant historically? He stresses the long-term nature of the task, estimating that it will take about 50 years to complete.

But in a decade’s time the detailed shape of this 18th-century estate will become much clearer. The park itself (cow-park and sheep-park) will be mown and perhaps returned to grazing. The perimeter woodland will be managed to form the natural frame for the park, so that the eye is drawn from the house to the distant vista of the Firth of Forth, North Berwick Law and, less fortunately, to Cockenzie Power Station.

Hidden features will start to emerge - the ruins of an 18th-century dovecot, an amazing shell-grotto, a tea-house, ice-house, fruit store, flower garden (with segmented borders), lake, obelisk, terraced walk and ha-ha. Roofless and, in some cases, vandalised outbuildings will be rescued, the canal will be reconstructed, terrace walks will begin to reappear from the impenetrable scrub and the flower garden will be planted.

It takes an act of imagination to picture all this and meticulous detective work to reconstruct the evidence. Newhailes is a place where time seems to have stood still, and now it is slowly coming back into circulation.

Newhailes is entered from the A6095 from Edinburgh to Musselburgh, one mile east of the Newcraighall exit from the A1 dual carriageway as it leaves Edinburgh. Its woodland and perimeter wall are on the left-hand side of the road just beyond the sign indicating that one has entered East Lothian and the townof Musselburgh. NTS currently operates a policy of open access to the grounds, which means that you are at liberty to explore. The house is not open to the public.