Outside the property has both covered and uncovered porches with a convenient poolbath overlooking the heated Gunite pool and spa framed by generous lawn and plantings offering views of the 13-acre reserve and beyond.
Castres' commitment was rewarded in the dying moments when Tillous-Borde went over in the corner, however the score was purely academic as Northampton closed out the game to ensure they became the first English team to record a 100% pool record since Bath in 2002.
The three-time European champions eased seven points clear in Pool 5 - closest challengers Bath visit Glasgow on Sunday - after subduing the spirited hosts.