This will last an hour. We find that if you tell your child that they are going to play and you're popping to the shops and will be back soon to collect them, helps the child to understand that you will return. This helps if it is transmitted with confidence to them as you know you will return and collect them, and that conveyed helps them embrace an experience of fun! This may really mean you stay in your car in the car park but in order for them to settle its good for them to know that you are leaving but coming back. Try and use a similar scenario, like when we go and visit granny and papa for instance.