5 year old stealing

[kennycat]

I'm at the end of my tether with my five year old son. I don't know what else to do. He is like a magpie. He digs around in drawers and cupboards he is'n't allowed in and takes things he likes the look of. Then lies about it. He doesnt' seem to care much about being told off or sanctions. He just rolls his eyes around in a weird way and kind of maniacally laughs a bit. It came to a head as we were at my mum's today and he did it there. She shouldn't have to babyproof her house for a five year old.
I didn't let him have pudding this evening to see if that worked and he didn;t like it but I'm not sure it's going to stop him.
Help! Any advice?

DS had to be frisked for a while every time he left nursery at school. He was stuffing cars he liked the look of into his pockets. I was mortified- the nursery teacher told me it’s perfectly normal and I shouldn’t worry. He had been to a private nursery before starting nursery at school and had never done it there, and had spent a couple of mornings a week at a play group and never done it. It was a weird phase -apart from the one time we arrived home from a tourist attraction, having spent money in the gift shop, to find he had stuffed a rubber and a pirate ring in his pocket Telling him we were either going to drive him straight back to hand them over and apologise or dad would take them to the local police station to hand them in and say sorry did the trick. He never did it again.