His descendant William Forbes, 7th Laird of Tolquhon (died 1596), began work on a new castle in 1584, retaining the Preston Tower but adding new, more comfortable accommodation.

An inscription on the gatehouse records that "AL THIS WARKE EXCEP THE AULD TOWR WAS BEGUN BE WILLIAM FORBES 15 APRIL 1584 AND ENDIT BE HIM 20 OCTOBER 1589".

[2] The home of a "Renaissance man", Tolquhon was designed for show rather than defence, and was the work of the mason-architect Thomas Leper or Leiper.

After William Forbes' death his descendants continued to occupy Tolquhon until 1718, when they were forced to move out due to debts incurred by the failure of the Darien scheme.

[4] The main entrance is on the north range of the castle, with the Preston Tower forming the north-east corner.