How was this error not picked up before being announced to the public?

I have seen some things in almost ten years as an on-course reporter for the Racing Post, but events at Nottingham on Wednesday have to take the biscuit.

For several minutes stalls handlers could be seen trying to help stricken horse Operative in stall 11, with the racecourse commentator name-checking the horse time and again.

Yet, somehow, instead of calling through number 17 as the horse to be withdrawn, the starter identified number nine, Magic Pulse, drawn in five and still out the back of the stalls at the time.