Paul Kewley, 38, was caught red-handed at the store last weekend on Sunday, October 5.
The defendant, of Medhurst Drive, Bromley pleaded guilty to theft and obstructing PC Aaron Richards in the execution of his duty.
He also admitted being in breach of a suspended prison sentence.
Kewley was locked up for six months by District Judge Sophie Toms at Newport Magistrates’ Court.
