a young man was banned from every branch of sainsbury 's after he was seen testing speakers on sale in a branch of the supermarket - even though he put the equipment back where he found it .
the giant firm sent him an aggressive letter warning that staff would call the police if they ever catch him trying to enter sainsbury 's .
mr gould , who has learning difficulties and is unemployed , went into the sainsbury 's branch in stoke-on-trent and opened two boxes containing £ 25 speakers that he then tested the gadgets to see if they worked with his mobile phone .