The incident happened when the victim parked his horse box at the car park on Wilton Road at around 10.20am on Tuesday October 13, 2009.
He returned at around 11.45am and discovered the white LDV 400 convoy box had been stolen.
The box contained a large quantity of tack and equipment worth a substantial value.
One of the three saddles stolen was a birthday present for his son.
It has a blue trim with the word ‘Ethan' on it in gold writing.
PC Paul Anderson, who is investigating both incidents, said:
"The victim is obviously very upset that his property has been stolen and is eager for its return.
"We would like to appeal to anyone who witnessed this theft to please contact police urgently.
"If you are approached by someone selling a horse box matching this description in suspicious circumstances, we would ask you to please get in touch."
Anyone with any information is asked to contact PC 1921 Paul Anderson on Leicester (0116) 222 2222, follow the instructions to leave a message for a police officer and when prompted key in the officer's identification number 1921.
Alternatively call Crimestoppers, anonymously, on 0800 555 111.