Grandouet remains on course for the Stan James Champion Hurdle at Cheltenham on Tuesday despite taking an alarming drift on the betting exchanges on Friday afternoon.
The six-year-old was forced out of the contest 12 months ago through injury, but made a pleasing return to action in the International Hurdle at Cheltenham in December.
He has not been seen in competitive action since and did suffer a minor training setback around a month ago.
Grandouet was a significant drifter in the Champion Hurdle market on Betfair, with his price briefly reaching 40/1 before stabilising, but Henderson did not report any problems after his charge worked in company with fellow Festival-bound stablemates this morning.
Speaking at Sandown, Henderson said: "Grandouet worked on the grass in the fog with Une Artiste and River Maigue. They went a good gallop and it was all good. The ground was beautiful.
"AP (McCoy) was also down, he rode Binocular, and Barry (Geraghty) schooled Simonsig and Riverside Theatre. They've virtually finished everything now."