In 1740, Hugh Smithson married Elizabeth Seymour, who, in 1750, inherited all the Percy properties. Smithson duly changed his name to Percy and was made the 1st Duke of Northumberland. The couple decided to make Alnwick their main home, which initiated a new phase in the development of Alnwick.
Within the town, maps from the 1780s show that houses were starting to occupy the tail end of burgage plots, and fill the gaps between the different settlements that had previously been separate. But for another century the outside boundary of Alnwick changed little.
The Freeman were still involved in running the town, building the Pottergate Tower in 1768, but increasingly, the Dukes of Northumberland were having an influence on Alnwick.
The Castle, which had been badly neglected, was restored in a ‘gothick’ style, while the North Demesne was remodelled by Lancelot ‘Capability’ Brown. This landscaping involved moving the Denwick road to the south of the Aln and building the Denwick Bridge to carry this new road over the river. The Lion Bridge was built to replace the medieval bridge which was destroyed by flooding in 1770.
Carriageways were built to allow the Duke and Duchess to enjoy their newly created landscape and a number of dramatic buildings were constructed, including the Ratcheugh Observatory and Brizlee Tower.
In 1800 the 2nd Duke of Northumberland acquired Alnwick Abbey, which he promptly dismantled, apart from the Gatehouse, which was refurbished as the entrance to Hulne Park.
In 1821, the 3rd Duke built the Canongate Bridge which involved diverting the Wooler road upstream, and the Alnwick-to-Eglingham turnpike, inaugurated in 1826, made use of this bridge.
Differences between the Duke and the Freemen over the ownership of the Moor resulted in a series of costly lawsuits, and some re-alignment of the boundary between Hulne Park and Alnwick Moor.
As well as changes to their properties, the Dukes were increasingly investing in amenities for the town including pants on Bondgate Without and the Northumberland Hall.
Other new organisations included the House of Correction, Dispensary and Parish Poor House.
At the same time, the local main roads were being improved using methods pioneered by McAdam and Telford, while the Turnpike Acts provided for a system of tolls for improvement and maintenance. These improvements made the movement of people and goods more efficient and Alnwick became an important staging post on the Great North Road.
The coming industrial age was presaged with the building of a wagonway bringing coal from the new mines at Shilbottle to Alnwick.